Summary of Global Warming

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 & methane (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 further.  (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, in the case where we ramp down our emissions only slowly, 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 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.

     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 low on 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, Pakistan and India will be especially hard hit this century.

     With less food and water - petty and not-so petty crime, ethnic riots, small wars, 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 farther; in many areas, they are cheaper than fossil-fueled electricity.  That is, the net cost of greening our 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 (same $/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.

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