Distant Past

     Dr. Fry’s analysis is based most of all on the Vostok ice cores over the past 430,000 years.  And on other researchers’ findings on conditions some 4 and 14 million years ago.  See above, but below notably Tripati 1209, Csank 0311, Pagani 1209, and Shevenell 0208.

Long-Lost Greenland Ice Core Suggests Potential Disastrous Sea Level Rise 0723 - Much of Greenland was ice-free around 416,000 years ago.  Thus, Greenland has not been frozen for a million years.  As the scientists started to sieve it to separate out the sediment, they were surprised to see twigs, mosses, leaves and seeds.  “We have a fossilized frozen ecosystem here,” said Bierman, “And what that meant, of course, is the ice sheet had gone away, because you can’t grow plants under a mile of ice.”  The potential implications for sea level rise are enormous, said a co-author, probably 10s of meters.

‘We are damned fools’ - Scientist Who Sounded Climate Alarm in 1980s Warns of Worse to Come 0723 - Dr. James Hansen and others interviewed.  The world is moving towards a “new climate frontier”, with temperatures higher than at any point over the past million years....  This is due to what Hansen said was an “unprecedented” imbalance in the amount of energy coming into the planet from the sun, versus the energy reflected away from Earth....  As heat waves strafe populations unacustomed to extreme temperatures, forests burn, and marine life struggles to cope with soaring ocean heat, the current upward spike is occurring at a pace not seen since the extinction of the dinosaurs 65 million years ago....  It's the rate of change that's the issue.
    We have been staring this in the face as scientists for decades, but now the world is going through that same process, which is like the 5 stages of grief, another scientist said.  “It’s painful to watch people go through it.  “But we can’t simply give up because the situation is dire,” Huber added.  “We need to say ‘Here is where we need to invest and make changes and innovate’ and not give up.  We can’t just write off billions of people.”

Labels in chart (10, 20, 30, 31, 44, 52, etc.) indicate specific age bins, in millions of years.

What Lessons Can We Learn from the Last Great Cooling-off Period? 0522 - The story involves volcanoes, the oceans, variation in the sun’s output, and depopulation in the Americas from germs brought by Columbus and his successors.

Global Warming 55 Million Years Ago Could Hint at Our Scorching Future 0821 - Methane hydrates from the ocean floor unleashed average global surface tremperatues 11°C hotter than today.  Consequences included hungrier insects, oceanic extinctions, rapid evolution, shrinking mammals, and strange new rains (water vapor transport from equator to poles) and danger zones, as ocean oxygen levels plummeted.

The Alarming Power of Melting Arctic Ice 0621 - At least 25 times in the past 120,000 years,  Dansgaard-Oeschger events warmed Greenland more than 10°C in just a few decades.  Widespread and rapid melting of ice in the Greenland, Norwegian, and Iceland Seas seem to have preceeded these rapid meltings.  This sea ice melting allowed warm Atlantic water to penetrate northward, triggering or amplifying the warming air around Greenland.

Study Finds 6°C Cooling on Land during the last Ice Age 0521

11 of 12 Hottest Years Have Occurred since 2000 - 0420 - "The last time the CO2 was this high was during the Pliocene, [around] 4 million years ago.  Then temperatures were 3-4°C warmer than now and sea level was 20-30 meters higher."

Antarctica Had a Polar Rainforest when Dinosaurs Roamed 0420

A World of Searing Heat and Melted Ice Caps - Climate Model of Early Eocene Is ‘Scary Finding’ for Earth’s Future 0919 - PETM 55 million years ago, and surrounding few million years.  Global surface was 14°C hotter than now.

CO2 Levels at Highest for 3 Million Years – When Seas Were 20 Meters Higher 0419 - take 1 on study

The Last Time CO2 Levels Were This High, Trees Grew at the South Pole 0419 - take 2

Rise of CO2–Absorbing Mountains in Tropics Set Thermostat for Global Climate? 1218

Global Warming - Worrying Lessons from the PETM Past 0918 - 5 to 8°C global warming in only 10,000 to 20,000 years.  Flooding increased 8- to 14-fold in the Pyrennes.  Fertile river plain turned into arid extensive gravel plains.  Sea surface temperatures reached 36°C [97°F] in places, a lethal temperature for many organisms.

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 1-3 centuries now.

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 lack of certain feedback processes, model-based climate projections may underestimate the long-term warming in response to future radiative forcing, by as much as a factor of 2, 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.”

We Have 5 Years to Save Ourselves from Climate Change – Harvard Scientist 0118 - highest CO2 in 12 million years, and 33 million years ago, ocean was 10°C warmer.

Dead Sea Warns of Unprecedented Drought 0317 - world 4°C hotter than now 115K years ago, Dead Sea rain down 80%

1815 Tambora Eruption Showed Disaster from Even Small Climate Changes 0117 - "year without a summer", widespread crop failures and spike in starvation.

History Reveals Greenland Ice Might Melt Much Faster Than Believed 1216 - ice-free 25% of last 1.4 million years

2 Million Year Record Indicates 5°C Warming from 400 ppm CO2, 9° from 560 ppm 0916 - take 1 on Snyder’s study.  Her study is the basis Dr. Fry uses to convert polar to global temperatures.

Earth Is Roughly Warmest in About 100,000 Years 0916 - take 2 on Snyder’s study in Nature

Human-Induced Climate Change Began Earlier than Previously Thought 0816

Earth Is Warming 50 x Faster than When It Comes Out of an Ice Age 0216

'Medieval Warm Period' Wasn't Global or Even All That Warm, Study Says 1215 - 900-1300 AD, peak ~ 950 AD

Unprecedented 21st Century Drought risk in the American Southwest and Central Plains 0215 - PDF

US 'at Risk of Mega-Drought Future’ 0215 - summary of the above.
    See Overviews page for an excerpt - using past to project the future.

Plio-Pleistocene Climate Sensitivity Evaluated Using High-Resolution CO2 Records - Martinez-Boti 0215 - PDF
        AFTER removing ice sheet change albedo effects, climate sensitivity across millions of years falls in the 1.5-4.5°C per doubled CO2 range used by the IPCC.

Climate Sensitivity in a Warmer World - Lea 2015 - PDF - response in journal to the above article

PETM Spike Driven by Massive Carbon Release over 2 Decades 1013 - PDF

3.5 MY Ago, Arctic Was Forested, Far Warmer 0513 

7 World Region Temps Back to 1 AD - JPG.  Graph is shown below.

Thawing Mosses Tell a Climate Change Tale 1117

Ancient Oceans Were Probably a Good Bit Cooler than Previously Thought 1017

Volcanic Eruptions Triggered Global Warming 56 Million Years Ago 0817

Earth Warmed between 1750 and 1880 - 0717

How Climate Change Strangled a Jurassic Ocean Ecosystem 0717

Earth Is Warming 20 times Faster than Its Fastest Natural Climate Change 0617

Humans Poised to Cause Earth’s Fastest Climate Change in 50 Million Years 0417

How the World Passed a Carbon Threshold and Why It Matters 0117

Climate Change May Be Escalating So Fast, It Could Be ‘Game Over’ 1116

Comet or Asteroid Crash May Have Heated Earth 56 Million Years Ago 1016

Earth Is Hottest in 115,000 Years, due to Human-Driven Climate Change 1016

Climate Data since Vikings Cast Doubt on More Wet, Dry Extremes 0416

Climate Change’s Toll Kept Early Dinosaurs from the Torrid Tropics 0615

Ice Cores Show 200-Year for North to South Pole Climate Lag 0515

Changes to Algae in Remote Andes Lakes Warn of Climate Change 0215

Humans Polluted the Air Long Before Industrial Revolution 0215

Man-Made Air Pollution Reduces Central America Rainfall 0215

Why Climate Scientists Are Right About How Hot Earth Will Get 0215

Ancient Climate Records ‘Back Predictions’ of Much Warmer from Current CO2 Levels 0215

Colorado Mastodon Bones Show Ancient Warmer Earth 1114

Scientists Probe Earth's Last Warm Phase (129-116 kya) 0414

Rapid Reductions in North Atlantic Deep Water During the Peak of the Last Interglacial Period 0214

Arctic Warmest in 120,000 Years 1113

PETM Spike Driven by Massive Carbon Release over 2 Decades 1013 - PDF

Warming Spike - Siberian Stalagmites Show Permafrost Peril 0613

Global Cooling as Significant as Global Warming 0613 

Prehistoric Window on Earth's Future 0413 

Late 20th Century Hottest in 1400 Year Record 0413

Arctic Summers Warmest in 600-Year Record 0413

Himalayan Adventure Foretells Climate 0313

Global Temperatures Highest in 4K Years 0313

Proxy Evidence for Warming Since 1800 0213

Underwater Forest Reveals Story of a Historic Mega Drought 1212

High Arctic Summers Warmest in 1,800 Years 0912

Last Time CO2 Levels Were This High 1009

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 long ice ages about 270 Mya.

Coupling CO2 to Ice & Sea Level Over 20 Million Years - Tripati 1209 - PDF - See figure below (part of Fig. 1 in article.)

Geologic Record & Climate Change - Patterson 0105 - PDF

Patterson re-makes the case (from 1991 and 1997 by Friis-Christensen and Svensmark) that warming (and cloudiness) in the past century has been tied to variations in solar output.
    However, at least 38% of annual sunspot numbers in Patterson's graph 1 (after 1934) appear too low (none shown as over 85, but 17 were actually over 100, including 4 over 149, and 1 over 200).
    The high correlation between solar irradiance and cosmic rays measured on Earth is to be expected, as the sun’s magnetosphere waxes and wanes, coincident with the sunspot cycle.
      Low clouds generally cool Earth; they correlate reasonably well with solar irradiance and cosmic rays.  However, not shown are high clouds, which generally warm Earth; they too vary with solar irradinace and cosmic rays, probably more strongly than low clouds do.
    This tends to [more than?] offset the cooling effect of more low clouds when cosmic rays increase.  That is, the cloud elevation difference explains why surface temperatures correlate poorly with cosmic ray flux variations.  But the correlation is much better before the human emissions component overwhelmed the solar the solar variation component of surface tempoerature change, that is before 1990 or 2000.

Patterson's graph for the North America temperature anomaly only.

     For perspective, see "∆T, CO2, SO4, Sun" under Temperature Analysis on the Data page.  Three files go thru 2004, 2009, and 2012.  Statistical ties to the sun grow weaker from the 2004 edition to the 2012 edition.  "Sun" there was sunspot number, not sunspot cycle length.

    Also, sunspot cycle length was 12+ years from the 2001 maximum to the next maximum, probably after 2013, suggesting 0.7°C cooling, much more than we've experienced.  Remember record US heat in 2012.  This suggests a greatly increased role for greenhouse gases, relative to changes in solar output, epsecially after 2000.

     Patterson's reasoning suggests the key role of a positive feedback loop, as permafrost thaws with warming, then adds carbon to the air.  Carbon additions to the air from permafrost in recent years have been comparable to those from US vehicles.  They are growing.

Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg/Ca and 18O/16O measurements on benthic foraminifera - Billups 0202 - PDF  - Temperatures related to ice volumes.

Fig. 1 - Records of key climate variables over the last 20 Myr.
    Forcing of the model are changes in the stacked benthic 6180 record with respect to preindustrial times (a, dark blue, Zachos et al., 2008).
    Output is a consistent record for the Northern Hemisphere temperature change with respect to pre-industrial conditions (b, green) and sea level (c, light blue).  The reconstructed CO2 record (d, orange) is obtained by inverting the relation between NH tem- peratures and CO2 data.  The ∂18O curve is smoothed in order to clarify the gradual decrease over time.  Atl data are available every 0.1kyr.  The thick lines represent 400-kyr running mean. Grey error bars indicate the standard deviation of model input and output. For CO2 the error bar is calculated as 400-kyr running mean, for the other records it is the standard deviation on the 0.1 kyr value as used in the model.

Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg:Ca and 18O:16O measurements on benthic foraminifera - Billups 0202.pdf

     Regarding solar output changes, in contrast to Tim Patterson's graph above for North America until 1990, Earth's total land surface temperature diverged strongly from solar output after 2001, except for 2013-15 and 2020-21.

Still, sunspot numbers during the satellite era, particularly their square root, correlate well with solar output.

Section Map: Heat