Many studies available below, especially those sponsored by governments, are reviews of a much larger literature. Their dozens (or hundreds) of authors (& editors) are expert researchers in their fields. Some reports are organized into chapters on different aspects of climate change. Almost all are in PDF format. More recent studies are listed above earlier studies. Page count is shown if 20 or more. Author(s) are identified, next to the date (mmyy), for studies by only one or a handful of researchers, or by an institutional sponsor.
Many of these overview studies are sponsored by governments and/or their agencies, notably the US, the UN (mostly, IPCC - Intergovernmental Panel on Climate Change), and the UK (England - especially the Stern Review). They are based on scores, hundreds, or thousands of studies, by several times that many researchers.
Each graph or map below comes from the document available immediately above it, except RCPs (under National Climate Assessment), which is drawn directly from Wikipedia, indirectly from Moss et al., 2008, and emissions underlying RCPs, drawn from IPCC 5, Tech Summary, further down page.
Topping the list, just below the COP21 Paris climate agreement of December 2015 are 4 studies that I deem key. 3 are about increasing droughts. 1 is about permafrost carbon emissions. Excerpts and summaries are included.
3 to 6 overview studies can be called books. 1st, NIPCC's 865-page compendium of research answers what "skeptics" see as inaccuracies, omissions, biases, and erroneous conclusions by the IPCC. 2nd, Lester Brown's book, Plan B (v. 2.0, 378 pp), reviews climate change and other problems, notably soil loss, groundwater depletion, food production plateaus, deforestation, overpopulation, overconsumption, and poverty. He makes many recommendations. 3rd, Nicholas Stern, former chief economist for the World Bank, with other research staff, prepared the Stern Review (711 pp) in 2006 for the UK Chancellor of the Exchequer. It appears in the Government Overviews sections. This website includes pieces of books: (4) 2014's US National Climate Assessment (> 1,000 pages) and (5-6) four IPCC Assessments over 11 years - but only pieces.
Following the sets of overview studies are relatively brief summaries, from the general scientific press, for some of them, as well as for several other reports, whose originals are not included here.
Near the bottom are my comments on the 2013 US draft National Climate Assessment. They point out what I see as some deficiencies and omissions, especially about future carbon emissions from permafrost and lack of attention to lessons from paleoclimate studies. Below those, at the bottom, is my assessment of the climate situation.
Near the middle of the page is a draft of the 2017 US National Climate Assessment. It mostly fixes the problems I identified in the 2013 edition.
Paris Climate Agreement Text 1215 - PDF, 31 pp
text highlights of the above, including (in PPT summary form)
more text highlghts of the above, again in PPT form
#3 Droughts thru 2008 & Extreme Droughts by 2030 - Dai 0111 PDF, 21 pp
Changes in the size of each Earth system carbon pool in response to the addition of permafrost carbon to the UVic ESCM. That is, the difference in the size of each carbon pool between simulations with and without permafrost carbon. All values are relative to the size of the frozen permafrost carbon pool. A summation of all the pools adds up to 100% for each year.
Results are given for two emissions pathways (DEPs 4.5 and 8.5) and for 3 climate sensitivities to a doubling of CO2 (2.0, 3.0, and 4.5°C). Soil layers that thaw, but are subsequently returned to a permafrost state, continue to be administered by the active soil carbon pool, leading to the apparent high rate of transfer of carbon to the active soil carbon pool in the 20th century.
Permafrost (not including whatever is under the ice in Greenland and Antarctica) holds about twice as much carbon as the atmosphere does today. In the worst case shown, if current net carbon sinks fail, atmspheric CO2 levels could more than double, even if humans ceased carbon emissions today.
In fact, the permafrost carbon pool is twice the amount of carbon now in the atmosphere. Putting 85% (680 ppm) of that in the air (worst-case scenario RCP 8.5) would almost triple (+170%) our current atmospheric CO2 level. That's on top of 820 ppm added from fossil fuels in RCP 8.5: in all, 1900 ppm of CO2 in the air by 2300.
The Great Transition - L Brown 2014 - 67 slides, about the transition from fossil fuels to renewables. The book is available at http://www.earth-policy.org/books/tgt/tgt_presentations.
Full Planet, Empty Plates - L Brown 0813 - PDF, 87 pp
Plan B v 2.0 - Lester Brown 0606 - PDF, 38 pp
Overview Studies, except Government
Climate Dominoes - Spratt & Dunlop 0522 - PDF, 23 pp
Heat Stored in the Earth System - Where Does the Energy Go? 0920 - Abstract. - von Schuckmann, Hansen et al. Earth gained 358 zJ over 1970-2018. This 48-year total is about 600 times annual human energy use, or 10-20 times cumulative human energy use. Over this period, the oceans account for 89% (52% in the upper 700 meters, 28% 700-2,000 meters deep, and 9% below that); land (continental crust) 6%; melting ice 4%; and atmosphere 1%. Over the shorter and most recent 2010-2018 period, these figures were 90% ocean (52-30-8%); 5% land; 3% ice; and 2% atmosphere. The rate of heat gain was 0.87±1.2 Watts / sq meter over 2010-2018. There have been various comparable estimates before and since, as shown in the diagram and spreadsheet below left. 0.47 in the diagram below right is for 1970-2018; 0.87 is for 2010-2018. In order to stabilize Earth’s surface temperature (at a level substantially higher than today’s unless all excess CO2 is removed immediately), Earth’s CO2 level must be reduced from 412 ppm to 353 ppm.
Earth Energy Imbalance Estimates, across Studies - spreadsheet summarizing studies cited in the paper and underlying the graph above left. Trend over time is shown by orange dots. 0.87 Watts / sq meter = 450 TW (million Watts) when summed across Earth’s surface. This 0.87 (450) rate is about 30 times the human rate of energy use now.
Heat Stored in the Earth System - Where Does the Energy Go? 0920 - PDF 29 pp, the main study, abstract above. Earth's heat gain rose to 0.87 W per sq meter, from 0.47 averaged over 48 years or (0.40 over 51 or 56 years). Earth's rate of heat gain has increased over time, as has Earth’s surface temperature (about ~2% of the heat gain). Excerpted figures are below. The gray one at right is about warming the ground / soil / rocks.
below, Optimum Habitality Zones maps first
historic map 1st, then ~2070 from RCP4.5, then (next row) ~2070 from RCP8.5
Graphs below are for high emissions scenario (RCP 8.5).
Weeks with temperatures > 95°F (max = 26 in AZ & S TX). Next below, days with wet-bulb temps > 82°F. 95°F is lethal. Max ~ 70 in LA.
Bekow, # of forest fires/year > 12,000 acres,2040-70
Below, % of properties below high tide in 2040-60
Crop Yields (Purple is reduced, green is increased.)
Economic Damages as % of GDP, from +0.6% to -59% (FL, etc.)
Climate Tipping Points — Too Risky to Bet Against 1119 - Rahmsdorf, Steffens, Schellnhuber, Rockström, et al.
9 active tipping points - Tipping points are probably being passed well before 2°C warming. This requires an emergency response. We face a series of cascading, interactive tipping points, starting from Arctic sea ice loss. Changes in (heat) forcing are much higher than ever before. We may be heading to CO2 levels last seen 50+ million years ago, with temperatures 12-14°C warmer than 1880’s.
Palaeoclimate Constraints on the Impact of 2°C Anthropogenic Warming and Beyond 0718 - PDF, 12 pp "Sustained warming at times over the past 3.5 million years has been accompanied by significant changes in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several meters on millennial timescales. Comparison of paleo observations with climate model results suggests that, due to the [models’] lack of certain feedback processes, model-based climate projections may underestimate the long-terms warming in response to future radiative forcing - by as much as a factor of two - and thus may underestimate centennial-to-millennial sea-level rise.
“Even if future emissions are reduced, warming will continue beyond 2100 for centuries or even millennia because of long-term feedbacks related to ice loss and the carbon cycle.”
The Uninhabitable Earth 0717
This is a summary of many, many studies, across many facets of climate research. It is based on interviews over the past several months with the most credentialed and tenured scientists in the field, few of them inclined to alarmism and many advisers to the IPCC who nevertheless criticize its conservatism. They "have quietly reached an apocalyptic conclusion, too: no plausible program of emissions reductions alone can prevent climate disaster.”
1. Doomsday - Peering beyond Scientific Reticence
“Fears of sea-level rise ... are barely scratching the surface of what [is] possible."
2. Heat Death - The Bahrain-ing of New York
3. The End of Food - Praying for Cornfields in the Tundra
4. Climate Plagues - What Happens When the Bubonic Ice Melts?
5. Unbreathable Air - A Rolling Death Smog That Suffocates Millions
6. The Perpetual War - The Violence Baked into Heat
7. Permanent Economic Collapse - Dismal Capitalism in a Half-Poorer World
8. Poisoned Oceans - Sulfide Burps off the Skeleton Coast
9. The Great Filter - Our Present Eeeriness Cannot Last
Note: This mixes technologies to put less carbon in the air, with social changes that correlate with fewer carbon emissions - with some overlap, and with a few technologies that remove carbon from the air.
Climate Risk in Southeast & Texas - Kinniburgh 0715 - PDF, 114 pp
Ice melt, sea level rise & superstorms - paleoclimate data, climate modeling & modern observations show 2°C global warming is highly dangerous - Hansen 0715 (draft) - PDF, 121 pp - multi-meter sea level rise, etc. by 2100 to 2200
The Conservative Case for a Carbon Tax - Taylor 0315 - PDF, 28 pp
EPA’s endangerment finding for CO2 will continue to stand up in the Courts. So the EPA is required to act, unless Congress changes the Clean Air Act to remove it from EPA jurisdiction. Democrats will continue to have at least 40 votes in the Senate to filibuster. So any CAA change requires Deomcratic buy-in.
A carbon tax is much more economically efficient than regulations - more CO2 reduced for far less $. It’s much more transparent than cap & trade, not subject to market swings and manipulation. It’s much better at protecting society’s wealth than alternative ways to cut CO2 emissions. With border adjustments, it protects jobs in a way that regulations cannot.
Many conservative Republican economists support a carbon tax, when it substitutes for other taxes. They include Alan Greenspan, Greg Mankiw, Art Laffer, Robert Samuelson, Charles Krauthammer, Richard Posner, George Schultz, Martin Feldstein, and Gary Becker, among others. etc.
Carbon Dioxide Removal and Reliable Sequestration - NAS 0215 - PDF, 155 pp
Soil lost 230 GT of carbon over the past 10,000 years, due to land conversion and land use. This comparesw to 365 GT added from burning fossil fuels. Feasible soil carbon sequestration, by moving carbon from the air back into soil, is estimated (to 2065) at 30-50 GT of carbon.
Other major methods to sequester significant amounts of carbon include accelerated rock weathering (almost as much potential), ocean iron fertilization (very costly, with 90-300 GT potential), bio-energy with carbon capture (100-1,000 GT), direct air capture, and sequestration for the 2 capture-only methods. Cost estimates range from $1 to $1,000 per tonne of CO2 removed, depending on the method, with wide estimates for each method.
Below, browns are drier than current “normal’. The center map measurs moisture in soil to a depth of 1 foot, the right-hand map measures it to 6.6 feet.
Referring to left-hand map, tan (Carolinas, Alberta) is “dry”. Light brown (-1 to -2: Iowa, Illinois, Alabama, Oregon, Ontario, etc.) is “moderate” drought. Semi-light brown (-2 to -3: Colorado, Texas, etc.) is “drought". Brown (-3 to -4: southern Mexico) is “severe” drought. Dark brown (-4 to -5) is “extreme” drought, and black is “exceptional” drought. These are AVERAGES - sometimes better, sometimes worse.
90% of California suffered extreme drought in 2014, and 60% suffered exceptional. All of Iowa and Nebraska suffered extreme drought in July 2012. So did almost all of Texas and most of Oklahoma and New Mexico, in July and August 2011.
The RCP 8.5 scenario is the fastest of 4 scenarios available - roughly “business as usual.” Global CO2 emissions have grown faster than that in the past 20 years, but show signs of slowing.
Days above 95°F will roughly triple. (See Figure 1, partly excerpted below.) This includes 75-100 such days a year for southern Illinois (Carbondale, Cairo, Vincennes, plus Decauter) and more than half of Missouri (St. Louis, Cape Girardeau, Joplin, Sedalia, Rolla, Poplar Bluff, Hannibal, etc.) It also includes Evansville IN and sliver of Ohio between Portsmouth and Marietta and Iowa north of Hannibal. This is almost as hot as Las Vegas.
The Midwest in particular will experience rising temperatures, in terms of warmer winters more than unbearable summers. But by the end of the century, the average Midwesterner will likely see 22 to 77 days per year over 95°F, compared to only 3, on average, over the past 30 years.
There is a 5% (or more) chance that 125-150 days a year will exceed 95°F in much the same area (plus Terre Haute and Jasper IN and Effingham IL, but minus Hannibal and Sedalia MO). See the rest of Figure 1 in the report.
These compare to 114 days above 95°F for Las Vegas in 2014, 95 such days in 2013, and 115 in 2012. The southern Midwest can become hotter than Las Vegas by the end of the century (or a little later), if current emission trends continue.
Below, based on current emission trends (maps from Figure 3 in the report), summers in Missouri, Illinois, and Indiana grow hotter by 2100 than Texas and Arizona ones today. Iowa and Ohio ones grow as hot as Texas ones now. Michigan, Minnesota and Wisconsin summers grow almost as hot.
At left mostly above (from Figure 4 in the report), heat stroke days will increase dramatically by the end of the century, from none now. Most of Missouri, Illinois and Indiana would suffer 40-60 days a year of dangerous heat: as bad (hot and humid) as anywhere in Texas. Ohio and Iowa would see 30-50 such days a year.
Worse, all of Illinois - and most of Missouri, Iowa, and Indiana - would experience 10-25 days a year of extremely dangerous heat: hotter (wet bulb) than anywhere in Texas.
In fact, “On our current path, the Midwest will likely see an average of as many as 3 days per year of Category IV conditions, which have never been experienced in the U.S. to date."
Agriculture will be harmed in a major way. Crop losses of 40-64% by 2100 are likely for corn in the Corn Belt and 8-38% by 2100 for soybeans in the same states (IA, IL, IN, OH, MO). The Corn Belt will have moved into Canada, North Dakota, and NW Minnesota. See maps and table below. In most of Missouri and Illinois, plus about half of Iowa and Indiana, crops losses are 25-50%, and worse in a few places. Wheat is much less affected, as it is often grown in the colder months and harvested by June.
4° Turn Down the Heat - Confronting the New Climate Normal - World Bank 1114 - PDF, 320 pp.
by the Potsdam Institute for Climate Impact Research and Climate Analytics
The report focuses on 3 regions: Latin America, the Middle East and North Africa, and Europe plus Central Asia. It says that 1.5°C warming above pre-industrial levels, by 2050, is locked in. According to the World Bank, with current policies, there is a 40% chance of Earth’s surface exceeding 4°C warming by 2100.
The Executive Summary says: "If the planet continues warming to 4°C, climatic conditions, heat and other weather extremes considered highly unusual or unprecedented today would become the new climate normal—a world of increased risks and instability.
"The consequences for development would be severe, as crop yields decline, water resources change, diseases move into new ranges, and sea levels rise. The task of promoting human development, of ending poverty, increasing global prosperity, and reducing global inequality will be very challenging in a 2°C world, but in a 4°C world there is serious doubt whether this can be achieved at all. [emphasis added]
"Immediate steps are needed to help countries adapt to the climate impacts being felt today and the unavoidable consequences of a rapidly warming world. The benefits of strong, early action on climate change, action that follows clean, low carbon pathways and avoids locking in unsustainable growth strategies, far outweigh the costs. Many of the worst projected climate impacts could still be avoided by holding warming to below 2°C. But, the time to act is now.”
It includes projections, for 2°C warming, of 30-70%, 50% and 60% yield declines for soybeans, wheat and corn respectively in Brazil, 50% for wheat in Central America and the Caribbean, and 10-50% for wheat in Tunisia. Similarly, the Balkans would face yield losses up to 50% for wheat, corn, vegetables and grapes. Crop losses would be nearly as great in Ecuador, Chile, and Syria. With "3-4°C warming, large negative impacts on agriculture can be expected.”
Rainfall is projected to decline 20-50% in a 4°C world for Central America, the Caribbean, the Western Balkans, and the Middle East and North Africa. Meanwhile, heavy rainfall and flooding would increase about 30% in Siberia and northwest South America. The Amazon rainforest could turn from a carbon sink to a source, as happened in the once-a-century droughts there in 2005 and 2010. Even with 2°C warming, carbon emissions from thawing permafrost could rise 20-30% across the forests of Russia.
One summary is available near the bottom of this page, as “Some Climate Impacts Unavoidable". Another is on the Costs, Wars+ page, Broad Impacts section.
A November 2014 study (see summary of the US portion near
bottom of this page: "US Can Slash Its Fossil Fuel Emissions 85% by 2050 - 1114.” The study suggests energy decarbonization paths for the top 15 CO2 emitting nations, mostly using available technologies.
Jointly, these 15 emit almost 75% of the world’s CO2.
Jointly (table at right) they could reduce CO2 45% by 2050.
Note India’s big increase. Most other nations cut big.
The Executive Summary for all 15 nations is here (PDF).
Individual nation study PDFs (not summarized) are below.
Living Planet Report - WWF 0914 Update - PDF, 180 pp. More excerpts than below are on Bio-Impacts page.
The global Living Planet Index (LPI) reveals a continual decline in vertebrate populations over the last 40 years. This global trend shows no sign of slowing down.
The weighted LPI (LPI-D) shows that the size of populations (the number of individual animals) decreased by 52% from 1970 to 2010. This includes 56% declines in tropical populations and 36% in temperate zone populations. It includes 39% declines for terrestrial species populations, 76% for fresh water ones, and 39% for marine ones. Populations in protected areas declined only 18%.
National Academy of Sciences Climate Change Summary - ongoing, link to WEB
Slides for Beijing - Hansen 0214 - PDF, 35 pp. This focuses on justice of developed nations using more than their share of Erath's carbon emission budget, and how the US and China can cooperate to reduce emissions to fit budget.
Assessing Dangerous Climate Change - Hansen 1213 - PDF, 26 pp
Quantifying the Influence of Climate on Human Conflict - Hsiang 0913 a meta-analysis of 60 studies
Many more graphs from the meta-analysis appear on the page "Costs, Wars+"
Rain (dryness) is a 2nd key factor: from Chinese dynasty changes, to Mayan, Akkadian and Angkor civilization collapses, to modern inter-group riots and conflicts in India, Brazil and Africa.
27 Climate Indicators over 43 Years - Amer. Meteorological Soc. 0813 - excerpt from below
Almost all of these indicator time-series graphs appear on other pages, beginning on the Heat page with cloudiness, then temperatures in the lower stratosphere, lower troposphere, and surface.
State of the Climate - American Meteorological Society - 0813 - link to website for study - PDF, 258 pp
Climate Impacts on Agriculture - Hatfield 0311 - PDF, 20 pp - This extensive literature review is the basis for the agriculture chapter in the draft 2013 US National Climate Assessment. See Food page for details.
The World on Edge - Lester Brown 0311 - 60 slides, as PDF
Climate Change in the Midwest - UCS 0809 - PDF, 24 pages
Average summer temperatures and rainfall for 1961-90, 2010-39, 2040-69 & 2070-99. Red is for the high emissions scenario, orange for the low emissions scenario. The data from these 2 climate migration studies can be extrapolated to other parts of the US.
1961-2003 in blue. 1993-2003 subset in magenta. Continents = soil and rock. Most temperature graphs are about air temperatures (Atmosphere). Note the dramatic increase in % heat going into oceans, vs everything else, during 1993-2003, compared to 1961-92: 91% oceans vs 9% everything else during 1993-2003, but 87% oceans vs 13% everything else during 1961-92.
Tipping Points Schematic
in Euros (€) per ton of CO2. 10 of 14 ways are identified to save money while saving energy and CO2.
Food Prices Soar - FAO 0408 - PDF, 44 pp. Graph below is from a later edition.
Meeting the Climate Change Challenge - Holdren 0108 - 26 slides, as PDF
Climate impacts now especially harm poor people: in Africa, Mideast, India, Indonesia, Peru.
Warming harms agriculture most & soonest in the tropics. CO2 fertilization effects are included.
Warming harms agriculture later in mid-latitudes. CO2 fertilization effects included.
Migrating Climates in the Northeast & Their Impacts - UCS 0707 - PDF, 160 pages
See Climate Change in the Midwest, above, for similar analysis of Great Lakes states.
Climate Wedges - WRI 0407 - PDF 20 pp
Overview Studies - US Government
Draft 4th National Climate Assessment - 0817: 13 US agencies and many universities, PDF, 545 pp
This edition substantially remedies the problems noted below in the 3rd edition, but still leaves room for improvement.
This draft edition has been reviewed by the National Academy of Sciences and other simiar groups, but the White House has not yet signed off on it. After the White House, it will be opened for public comment.
Among other things, the report says “Evidence for a changing climate abounds, from the top of the atmosphere to the depths of the oceans.”
“Many lines of evidence demonstrate that human activities, especially emissions of greenhouse (heat-trapping) gases, are primarily responsible for recent observed climate change…. There are no alternative explanations, and no natural cycles are found in the observational record that can explain the observed changes in climate. (Very high confidence)
“Even if humans immediately stopped emitting greenhouse gases into the atmosphere, the world would still feel at least an additional 0.5°F (0.3°C) of warming over this century, compared with today. The projected actual rise, scientists say, will be as much as 2°C.”
"During the Pliocene, approximately 3 million years ago, long-term CO2 levels were similar to today’s, around 400 ppm…. [G]lobal mean temperature in the Pliocene was approximately 2° to 3.5°C (3.6° to 6.3°F) above preindustrial , and sea level was somewhere between 20 ± 10 meters (66 ± 33 feet) higher than today.”
“[A]bout 17-14.5 million years ago", Earth’s "proxy-estimated global mean temperature" was "8°C ± 2°C [14°F ± 4°F] warmer than preindustrial… Geological proxies indicate CO2 concentrations of around 400 ppm ... suggesting that as yet unidentified feedbacks must be invoked to explain climate conditions.”
About 125,000 years ago [the Emian interglacial period], with greenhouse gas concentrations similar to preindustrial  levels, "global temperatures were … 1-2°C ... warmer than  levels" and "sea levels were 6-9 meters higher than modern levels”.
[Dr. Fry, this website’s author, says that the “unidentified feedbacks” from millions of years ago were largely albedo effects, changes in how much sunlight Earth reflects, much of it from less ice and snow, and probably more from reduced cloud cover and/or large-scale cloud structure changes, all multiplied by the greenhouse effect of more water vapor in a warmer atmosphere.]
US 2050 Decarbonization Strategy 1116 - PDF, 111 pp
Social Cost of Carbon, Update - US Interagency 0513 - PDF, 21 pp
Climate Change & Agriculture - USDA 0213 - 186 pp PDF, based on Hatfield's 2011 intensive literature review
Draft 3rd National Climate Assessment - Interagency 0113 - more than 1,000 pp
Individual chapters can be downloaded here from the NCADAC. Almost all chapters are also available below.
(China completed its most recent (2nd) national climate assessment at the end of 2011, with similar conclusions. A press summary is near the bottom of this page.)
Dr. Fry, in comments on the draft 3rd NCA, made several critiques:
1. It omitted paleoclimate data entirely, against which climate model output should be benchmarked. The paleoclimate data shows much more warming and sea level rise from current greenhouse gas levels than most climate models do.
2. It greatly underestimates the amount of warming still to come from albedo changes (such as melting ice to yield darker water) and other changes (e.g., warming the deep ocean to equilibrium with the top of the atmosphere).
3. It omits current and especially future carbon emissions from permafrost, methane hydrates, peat fires, etc.
4. It says far too little about active methods for CO2 removal from ambient air.
5. It should discuss climate change effects on agriculture after mid-century and sea level rise after 2100.
6. It should enumerate and discuss tipping points more.
Representative Concentration Pathways (RCPs) are needed to interpret the graphs below it. RCPs are newer scenarios than the IPCC used in 2007 (A2, B1, etc.) Caveat: these appear not to include positive feedback loops, especially carbon emissions from thawing permafrost.
Below: Fossil fuel carbon emission pathways for the CO2e levels above: IPCC 5 Fig. TS-19.
The inset graph relates RCP emission paths to ppm CO2 in the air.
4 RCP emission paths are shown: in billion tonnes (Pg) of carbon per year.
In RCP 2.6, net world CO2 emissions from fossil fuels peak ~2020, at ~10% higher than today's. They fall below zero ~2075. In this case, CO2 levels peak at ~450 ppm and fall to ~420 by 2100. Relative to 1901-60, the US has already warmed 2°F. We will warm 2°F more by ~2045, levelling off thereafter. In RCP 4.5, emissions peak ~2040, at 130% of today's, then fall to 60% of today's in 2080. CO2 levels rise to ~540 ppm. The US warms 4°F more by 2100.
Chapter 1 - Overview & Findings - PDF, 12 pp
In RCP 6.0, they peak ~2080, double today's rate, by fall to 140% of today's by 2100. CO2 levels rise to ~540 ppm by 2100 (and a good bit more after that). The US warms 5.5°F (3°C) from today by 2100, and still more thereafter. Hot!
In RCP 8.5, emissions only slow by 2100, when they are triple today's rate. CO2 levels rise to ~ 930 ppm by 2100 (then far higher). The US warms 9.5°F from today by 2100, then far more.
Dr. Fry: RCP 6.0 and esp. 8.5 would repeat conditions during the PETM 55 million years ago: an ice-free Earth, 10% less land, port cities under water, warm blood a disadvantage. Human work capacity falls 60+%, as US heat stress exceeds Sahara / Amazon today. See Bio-Impacts page, bottom 0213.
However, the world may be on track resembling RCP 2.6, a major change from the perspective 5-10 years ago. China’s emissions have plateaued, near their peak, while emissions have been falling in Europe and the USA for more than a decade. In 2021, Solar + wind + batteries are cheaper than coal and often natural gas for new power plants. In the USA at least, they afre also cheaper than continuing to operate coal-fired power plants.
By 2100, the likeliest sea level rise seems to be 1-4 feet.
But 0.66 to 6.6 feet is possible.
If seas continue rising at the current rate, they will rise 1 foot by 2100, so 0.66 feet (0.1 meter) would be a deceleration. 6.6 feet is 2 meters.
Chapter 2 - Our Changing Climate - PDF, 49 pp
2071-2099 Average, Less 1971-2000 Average - for 2 RCPs
Precipitation changes do not include evaporation changes. Thus changes in soil moisture skew drier.
1991-2011 Average, Less 1901-1960 Average
1971-2000 Baseline, versus 2041-70 and 2071-2100 .
Chapter 3 - Water - PDF, 44 pp
Chapter 4 - Energy - PDF, 17 pp
Chapter 5 - Transportation - PDF, 20 pp
Chapter 6 - Agriculture - PDF, 25 pp
Chapter 7 - Forests - PDF, 20 pp
Chapter 8 - Ecosystems - PDF, 25 pp
Chapter 9 - Human Health - PDF, 37 pp
Chapter 10 - Energy, Water & Land - PDF, 25 pp
Chapter 11 - Urban Systems - PDF, 15 pp
Chapter 13 - Land Use & Cover - PDF, 15 pp
Chapter 14 - Rural Communities - PDF, 15 pp
Chapter 15 - BioGeoChemical Cycles - PDF, 19 pp
Chapter 16 - Northeast - PDF, 25 pp
Chapter 17 - Southeast - PDF, 22 pp
Chapter 18 - Midwest - PDF, 23 pp
Chapter 19 - Great Plains - PDF, 21 pp
Chapter 20 - Southwest - PDF, 25 pp
Chapter 21 - Northwest - PDF, 27 pp
Chapter 22 - Alaska - PDF, 23 pp
Chapter 23 - Hawaii & US Islands - PDF, 20 pp
Chapter 24 - Oceans - PDF, 22 pp
Chapter 25 - Coastal Zones - PDF, 40 pp
Chapter 27 - Mitigation - PDF, 22 pp
Science Supplement Details - PDF, 55 pp
Topics for Future Assessments - PDF, 2 pp. Economics Analyses, National Security, Adaptation-Mitigation Interaction
Frequently Asked Questions - PDF, 31 pp
80% Renewables by 2050 - NREL 1012 - volume 1 - PDF, 286 pp
US Climate Indicators - EPA 0410 - PDF, 80 pp
US Climate Impacts - NOAA 0609 - PDF, 196 pp
Overview Studies - IPCC
IPCC AR6 Impacts Summary 0222 - PDF, 35 pages
IPCC AR6 Science Summary 0821 - PDF, 42 pages
2018: IPCC on 1.5°C vs 2°C and 12 Years to Go, 1018 Exec Summary - PDF, 34 pages
2014: IPCC 5 Synthesis Report 1114 - PDF, 116 pp
2014: IPCC 5 Impacts Summary - PDF, 44 pp
IPCC 5 Crop Impacts - PDF, 82 pp
Above are bars showing % of the 56 or more studies considered that found various % yield changes (color key at right). The black horizontal bars show the line between yields higher than now and lower ones. Farther into the future, more and more studies project lower yields, especially much lower yields. Assumptions about adaptation, CO2 fertilization and other matters varied from study to study.
2013: IPCC 5th Science Assessment - Technical Summary - PDF, 84 pp
Forecast Changes as Fraction of Global Mean Change (below). CMIP3 models are vintage ~2004, while CMIP5 models are vintage ~2011. Relative temperature changes on 97% of land exceed mean global temperature changes (red, dark red & purple), especially in the Arctic, while relative changes over 92% of the oceans (not the Arctic) are less than mean global temperature change (orange & light orange). Temperatures change more toward the poles.
These are relative to the global mean. For absolute projections of temperature change,see the maps from the 2014 Impacts summary, a bit above the 2013 Science Assessment.
That is, land surfaces warm faster than ocean surfaces.
Precipitation changes, however, are location-specific % changes relative to now. Increases will be strongest in the Arctic, while decreases will be greatest around the Mediterranean.
Permafrost loss could be as high as 88% by 2100 in the highest emission scenario.
Below, CO2 removal processes cannot keep up with huge, swift CO2 injections. Removal goes much slower, %-wise.
IPCC 5th Science Assessment - Exec Summary - PDF, 36 pp - figures missing; figure captions only
2012: Extreme Weather Events & Climate: Summary of Policymakers - PDF, 20 pp. Some diagrams are larger on web.
2007: Summary for Policy Makers - PDF, 22 pp
Science Summary - PDF, 21 pp
Damages Summary - PDF, 23 pp
Mitigation Summary - PDF, 35 pp
Overall Summary - PDF, 23 pp
2001: Agriculture and Ecosystems - PDF, 108 pp
Water - PDF, 43 pp
Overview Studies - Other Governments
Groundwater Trends - UNESCO 0712 PDF, 44 pp
Climate Change Compendium - UN 0909 - PDF, 70 pp
Stern Review (UK, Nicholas Stern ed., 1006 - 711 pp)
Executive Summary - PDF, 27 pp
Part I - Part 1 - Climate Change, Our Approach - Introduction
1 - The Science of Climate Change - PDF, 21 pp
4 - Implications of Climate Change for Development - PDF, 30 pp
5 - Costs of Climate Change in Developed Countries - PDF, 21 pp
6 - Economic Modelling of Climate-Change Impacts - PDF, 25 pp
Nor do they account for changes in Earth’s albedo (how much sunlight it reflects.)
9 - Identifying the Costs of Mitigation - PDF, 28 pp
13 - Towards a Goal for Climate-Change Policy - PDF, 25 pp
Note: Paleo-climate studies indicate that eventual temperature change for given CO2 levels will be substantially higher than shown here.
Part IV - Policy Responses for Mitigation
16 - Accelerating Technological Innovation - PDF, 30 pp
17 - Beyond Carbon Markets and Technology - PDF, 26 pp
Part V - Policy Responses for Adaptation
22 - Creating a Global Price for Carbon - PDF, 23 pp
27 - Conclusions PDF
Summaries (mostly by the Press)
Humans Started a New Geologic Era, the Anthropocene, in 1950 - 0723 - Some debate about exactly when, much less where. Based on nuclear fallout, industrial chemicals such as pesticides and plastics, as well as rapid atmospheric GHG growth and warming from fossil fuel use.
Climate Change Threatens ‘Things Americans Value Most,’ U.S. Assessment Says 1122 (National Climate Assessment) - “Over the past 50 years, the U.S. has warmed 68% faster than the planet as a whole,” the report finds. It noted that the change reflects a broader global pattern, in which land areas warm faster than the ocean, and higher latitudes warm more rapidly than lower latitudes. That shift means significant parts of the country now must grapple with growing threats to safe drinking water, housing security and infrastructure. A hotter atmosphere creates a litany of health hazards, makes farming and fishing more difficult and unpredictable, and imperils key ecosystems.
The frequency of billion-dollar disasters has now increased from once every 4 months in the 1980s to once every 3 weeks in the present. It finds that the United States is experiencing some of the most severe sea-level rise on the planet.
In the short term, the assessment finds, communities must do more to adapt to the changes that already are here — and some are doing just that. But over the long term, the only real solution is for humanity to muster the political and technological will to stop polluting the atmosphere.
Stifling heat waves in the Midwest to deadly floods in the Southeast, from warming oceans along the Northeast coast to raging wildfires in the West.
A warming world threatens reliable water supplies. Deluges and drought. Climate change is making our food, water and infrastructure worse. Droughts are projected to increase in intensity, duration and frequency, mostly in the Southwest.
Extreme events are wreaking havoc on homes and property. The United States has experienced an average of 7.7 billion-dollar disasters annually over the past 4 decades. In the past 5 years, that average has jumped to nearly 18 events each year, or about one every 3 weeks. Those disasters also don’t hit all Americans equally. Homes with poor insulation or inefficient cooling can make it harder for low-income residents to heat or cool their homes.
The U.S. can expect more forced migration and displacement.
Climate change is a growing public health threat.
It’s not just humans who are feeling the effects.
There is good news and opportunity to still shape the future.
World on Brink of 5 ‘Disastrous’ Climate Tipping Points 0922 - collapse of Greenland ice cap, collapse of main North Atlantic current (Gulf Stream +), disrupting rain for billions of people, and abrupt thaw of permafrost, and dramatic changes to vast northern forests.
How Not to Solve the Climate Change Problem 0722 - by Kevin Trenberth, a leading climate scientists for 4 decades who helped write IPCC assessments. in Dr. Fry's eyes, his influence exceeded only by Jim Hansen.
Paraphrasing: We are well on the way to 1.5°C hotter than 1880; damages will get even worse above 1.5°C. We need net-zero by 2050 to limit warming to 2°C. The changeover to renewables has been slow. Solar radiation management (SRM), by imitating major volcano eruptions, has the bad side effect of moving monsoon rain offshore. It is also expensive. [false] For CO2 removal (CDR), CCS (Carbon Capture - from smokestacks - and Storage) has proven to be too expensive - as well as ineffective, because it is mostly used for enhanced oil recovery. Direct air capture (DAC) is also too expensive so far, as it uses a lot of energy. The cost of removing our legacy CO2, even at a hoped-for $100 / ton, would exceed the Gross World Product (GWP). Trees are cheaper, but impermanent; forests burn. “The arithmetic highlights the tremendous need to cut emissions. There is no viable workaround.”
Dr. Fry’s comments: Achieving net zero would be wonderful, but it is very far from sufficient to hold global heating to 2°C. When Earth last wore 420-470 ppm CO2, millions of years ago, global temperatures were 4-8°C above 1880’s. This further (past and future, beyond 2°C) heating was, is and will be driven mostly by feedbacks from albedo (reflectivity) changes from snow, ice, and sulfates, plus their water vapor and clouds multiplier. The impacts of 5°C are far worse (several multiples of world GWP) than the cost of SRM and CDR. We indeed have a tremendous need to cut greenhouse gas (GHG) emissions, but cutting them to zero, even immediately, is way not enough. Small companies, recent start-ups, are devising ways (no fans, no heat to regenerate catalysts) to cut DAC energy use (and cost) by 95% or so. For SRM, the costs are measured in billions rather than trillions of dollars. Perhaps better SRM than imitating volcanoes is marine cloud brightening (MCB), targeted in the Arctic. There, warming has caused the polar jet stream to meander, bringing long dry hot spells, long rainy spells (floods), and deep excursions of polar air into temperate zones in winter. MCB probably would not affect monsoons much.
‘Soon the world will be unrecognizable’ – Is it still possible to prevent total climate meltdown? 0722 - This summary of Bill McGuire’s book, Hothouse Earth, mentions netither CDR nor SRM [see above]. If one throws away these tools, McGuire’s analysis is broadly correct. But we should not throw them away.
The Crucial Ingredients for Decarbonizing and Safeguarding Cascadia 1221 - Decarbonize electricity and electrify everything, plus other actions
It’s Grim 0821 - take 2 on IPCC's 6th Assessment, part 1
Major Climate Changes Inevitable and Irreversible – IPCC’s Starkest Warning Yet 0821 - take 1 on IPCC's 6th Assessment
Critical Measures of Global Heating Reaching Tipping Point 0721 - Some 16 out of 31 tracked planetary vital signs, including greenhouse gas concentrations, ocean heat content and ice mass, set worrying new records.
Yep, It’s Bleak, Says Expert Who Tested 1970s End-of-Civilization Prediction 0721 - Limits to Growth, from 1972. An update study shows that the 1972 study was essentially on target. It finds that, coming amid a cascade of alarming environmental events, from western US and Siberian wildfires to German floods, and the Amazon rainforest may no longer a carbon sink. Herrington’s work predicted that the collapse of civilization could come around 2040, if current trends held.
The other scenario, "comprehensive technology, modeled stalled economic growth without social collapse. Both scenarios “show a halt in growth within a decade or so from now…. pursuing continuous growth is not possible.”
Engineers - You Can Disrupt Climate Change 0621 - About 85% is about the challenges of decarbonization, 12% about those of CO2 removal (to 350 ppm or less) and 3% of solar radiation management. Carbon pricing is addressed up front. Decarbonization challenges addressed are especially the more difficult energy uses: aviation fuel; the production of metals; industrial process heat for cement, fertilizer, glass, etc.; infrastructure such as sewage; energy sources from advanced photovoltaic and batteries to advanced fission and fusion. Some CO2 removal methods need good engineering, as done subterranean disposal. More white surfaces can help with the “3%" solar radition management needed.
You can find one general summary of gloabl warming and climate change at www.tomorrow.io/weather/blog/global-warming-status/. It takes 15-30 minutes to read. I have only a handful of quibbles with what it says.
What's the Hottest Earth Has Ever Been? 0620 - 3,700°F in Hadean era, not long after formation of Earth, in the aftermath of the Moon's formation. Since Snowball Earth about 800 million years ago (Mya), Earth's surface temperatures reached around 90°F repeatedly, as recently as 92 Mya. 73°F during PETM, 55 Mya. Earth's surface is currently near 60°, during an interglacial, but with much ice still at both poles. Earth has rarely been as cold as the ice ages of the past 2-3 million years, since about long ice ages about 270 Mya.
Climate Worst-Case Scenarios May Not Go Far Enough, Cloud Data Shows 0620 - climate sensitivity about 5°C for doubled CO2, not 3°.
As the World Warms, Clouds Could Disappear 0319 for rapid acceleration of global heating.
What Would An Effective Solution To Climate Change Look Like? 0119 - local, regional or corporation, (inter) national
Scientists Have Uncovered a Disturbing Climate Change Precedent 0818 - PETM 55 million years ago. Temperatures were 10-15°C higher than now in Europe and New Zealand, with 40°C (104°F) heat waves for weeks at a time, actually normal for the PETM days. The tropics may have been a dead zone, with temperatures over 50°C (122°F) over much of Africa and South America. Tapirs lived near the North Pole and alligators on Ellesmere Island on the Arctic Ocean. Sea surface temperatures may have been 30°C (86°F) on the Antarctic coast. CO2 levels then were around 1,000 ppm. Changes to those conditions took place over 100s of 1,000s to millions of years; they may take only a century or three now.
Earth at Risk of Becoming ‘Hothouse' if Tipping Point Is Reached 0818 - amplifying feedbacks mentioned include permafrost thaw; loss of seabed methane hydrates; weaker land and ocean carbon sinks, starting with forest dieback and increased bacteria respiration; loss of Arctic summer sea ice; reduced Antarctic sea ice; and loss of polar ice sheets.
“To reverse the potential domino effect … requires … improved forest, agricultural and soil management; biodiversity conservation; and technologies that remove CO2 from the atmosphere and store it underground.... More broadly, “collective human action" is required to steer us a way from this potential threshold: "decarbonization of the global economy, enhancement of biosphere carbon sinks…."
7 Megatrends That Could Beat Global Warming - 'There Is Reason for Hope’ 1117 - less meat, renewables, no more coal, electric vehicles, batteries, efficiency, reforest
Methods for Climate Restoration 1017
What is needed (technologies & $/Ton) to get atmospheric CO2 down to 300 ppm, for 0° warming
Case for Climate Change Grows Ever Stronger 0817 - one take on the study above
New Climate Change Report Likely to Be Ignored to Death 0817 - another take - Trump administration “action"
James Hansen Just Outlined an Alarming Scenario for Our Planet’s Future 0715
summary of PDF much farther up the page. Many-meter sea level rise by 2100 or 2200, shut down much ocean circulation.
Climate Change Could Hammer Iowa Agriculture, Manufacturing 0115 - Iowa-centric take on same study
This picture is from a piece of land (left side) in Africa managed with Holistic Management grazing practices, used by locals taught by the Savory Institute. It stores far more carbon (and water) than land not so managed (right side of fence).
US Climate Assessment Warns of 10°F Warming by 2100 - 0113
1993-2012 US pace was +12°F / century
China’s National Assessment Spells Out “Grim" Climate Change Risks 0112 - from the 710-page report:
“China faces extremely grim ecological and environmental conditions, under the impact of continued global warming and changes to China's regional environment.” Assuming no measures to counter global warming, grain output in the world's most populous nation could fall from 5 to 20% by 2050. "But steadily, as the temperatures continue to rise, the negative consequences will be increasingly serious…. For a certain length of time, people will be able to adapt, but costs of adaptation will rise, including for agriculture.”
"Climate change will lead to severe imbalances in China's water resources, within each year and across the years. In most areas, precipitation will be increasingly concentrated in the summer and autumn rainy seasons, and floods and droughts will become increasingly frequent…. Without effective measures in response, by the latter part of the 21st century, climate change could still constitute a threat to our country's food security,"
Here's a simple video about risk of taking action vs not taking action.
And here is a simple stick-figure cartoon video about how warming happens and what its effects are and WILL BE. It's titled "Wake Up, Freak Out".
Gene Fry's Comments on the draft 2013 National Climate Assessment
re Ch 2 - Our Changing Climate 0613 esp. permafrost, also Arctic sea ice volume and paleoclimate, require reality checks. The Assessment is deficient for being inconsistent with these realities.
Summary of Global Warming - Gene Fry
Albedo Changes Drive 4.9 to 9.4°C Global Warming by 2400 - Fry 1220, PDF 15 pages (journal as published)
Albedo Changes Drive 4.9 to 9.4°C Global Warming by 2400 - MS Word, journal format, 15 pages October 2020
The evidence is overwhelming that humans have greatly accelerated natural climate change. Not only have we cancelled the next ice age, we are warming Earth's surface (and acidifying its oceans) far faster than at any other time since the dinosaurs vanished.
The last times CO2 levels were as high as today's (almost as high 4.0-4.2 million years ago, and a little higher 14-14.5 million years ago), air at the surface was averaged 7 and 10°F warmer than today, while seas were 65-130 feet higher. The CO2 & CH4 to temperature relationship from the ice cores is highly consistent with the observations from 4-4.2 and 14-14.5 million years ago. They portend a world 7 to 11°F warmer than today’s - from current CO2 and CH4 levels.
That's once the positive (amplifying) feedbacks from shrinking sulfate emissions, sea ice, snow cover, cloud cover, and land ice have played out. Also more water vapor, a key greenhouse gas, fits in warmer air, warming Earth’s surface further.
Cloud cover change is complex: cloud area coverage shrinks while high (warming) clouds increase and low (cool, rain) clouds decrease, both warming Earth. However, clouds (on average, especially low ones) become more opaque. This partially offsetts warming from the area and altitude changes. Moreover, the oceans must warm to match the new CO2 levels. Over time, warming oceans give some heat back to the air.
Warming over 1975-2016 from these factors was 2/3 as much as the direct effect from non-H2O greenhouse gases (mostly CO2 and CH4). However, future warming from these factors will exceed the direct effect from CO2 and CH4, by a factor of 3 or more. This is due both to accelerating (mostly albedo) feedbacks and shrinking future human emissions.
Warming, as ice core records tell us, drives higher CO2 and CH4 levels in the air. (See Home and Heat pages.) But CO2 and CH4 in the air also cause warming. This is called a amplifying (positive) feedback loop. Natural CO2 and CH4 come mostly from thawing permafrost, methane hydrates, faster respiration by soil microbes, and thinning (and burning) forests. Degassing carbon from oceans is also significant, and may become much more so as they warm. (Warmer water makes gases less soluble.) Also significant were methane leaks from coal mines (prominent after 1800) and oil/gas wells.
Arctic permafrost, a type of soil, holds about twice as much carbon as the air. Carbon emissions from permafrost (and methane hydrates) can warm Earth’s surface (and deeper oceans) several °F more, for a total of perhaps 18°F, or even more, warmer than today. Amplifying feedbacks are a HUGE problem. So, quitting human GHG emisions cold turkey is not enough to keep GHG levels as low as they are now. Far from it! And even if GHG levels level off, temperatures will continue to rise (quite a bit), until equilibrium is reached. This makes it all the more important to not only cut CO2 and CH4 emissions to almost zero ASAP, but to remove 3/4 of the CO2 and all of CH4 we have put in the air in the last 2 centuries. Earth’s remaining carbon budget is FAR less than zero.
With more warming, we will see more intense versions of the same weather extremes we have experienced in recent years: longer, drier, hotter droughts and more intense rainstorms (some hurricanes), with bigger floods. Over decades to a few centuries, more places on more days will become too hot and humid for humans to survive: i.e., more deaths from heat waves. That may include most of Georgia, Alabama, and South Carolina by 2100. Think Florida in summer, but much more so. Recent temperatures of 98°F in Alaska, 101 north of the Arctic Circle in Siberia, and 121 in British Columbia are a foretaste of things to come.
Sea level rise will accelerate, from 5-8 inches per century during the 1900s and 13 inches per century today, to perhaps 100 inches per century, the rate from 15,000 to 14,000 years ago. Ice loss has been accelerating by 12% per year (Greenland and Antarctica) recently. However, reaching a 5 feet sea level rise per century rate will take decades. 8.3 feet (100 inches) per century will take longer. But we are already committed to many meters of sea level rise. Goodbye Miami - and Norfolk and Sacramento.
The effects of warming (with droughts and floods) and CO2 fertilization on food supplies will interact with rapid groundwater depletion, which is now well under way in much of India, China, the US, and elsewhere. World food production could fall a lot over the 21st and 22nd centuries. It will not help that some of America’s crop-growing heartland is on pace to become as hot as Las Vegas around 2100, joined by a good bit of the rest by 2200. The same effect plays out across the globe. When heating runs out of water to evaporate, it raises air temperatures instead.
Moreover, as stated above, as Earth’s surface warms up further, larger and larger sections, especially during summer months, will become too hot for humans to survive outdoors, at least for long. This problem, beginning in the Persian Gulf, theatens to become quite noticeable by 2100 and widespread by 2200. Iran, Iraq, Pakistand and India will be especially hard hit this century.
With less food and water - petty and not-so petty crime, ethnic riots, small wars and civil wars, and terrorism will continue to increase. Tropical diseases will continue to spread, and faster. A large fraction of species will go extinct. Life for humans will grow worse. Poor people - especially foreigners - who emitted very little CO2, get hit earlier and harder. They try to escape to cooler areas, such as the USA and Europe.
The costs of warming are high: already some $600 billion per year. They will grow. The present value of future climate change damages, by one estimate, is about 1.5 times the Gross World Product. The cost of action to slow warming is much less. Some of the costs of action - energy efficiency - are negative. Prices for wind power have fallen a lot and solar power even faster; in many areas, they are cheaper than fossil-fueled electricity: the net cost of greening the electricity is negative. The prices of storage to deal with their intermittent power have also been falling fast.
We should do what we can to avert such a bad future. The 1st step is reducing carbon emissions, to almost zero. A tax on carbon emissions is the best policy to make that happen. This is especially important for industrial processes, aviation and shipping, and businesses more generally. The 2nd is to take carbon OUT of the air, much faster than we are putting it in, ASAP. The 3rd, if we wish to hold warming below 2°C is solar radiation management, by reflecting sunlight away from Earth’s surface.
A price on carbon is needed to provide financial incentives to take carbon out of the air. Carbon can be stored in a combination of soils, biomass, rock, and ocean sediments. We Americans need to persuade our leaders to put a price on carbon, via a carbon tax - with a credit (= $/ton) for moving carbon FROM the air back into the ground (and into other carbon reservoirs). China, like parts of the US, has already begun the process of pricing carbon. Both trail Europe, whose carbon cap & trade policies for 15+ years have pushed emissions down 35-40% in the UK, Germany and elsewhere. Exxon and Shell assign a price to carbon ($60-80 per ton). European oil companies ($30-40/ton) called for a worlwide carbon price, as did the 25-year CEO of Walmart and several Republican statesmen.