Natural Climate Change

Earth's climate has been changing for hundreds of millions of years (MY).

It will continue to do so.  Climate change is nothing new.

     However, current warming is 7-30 times as fast as the previous fastest warming in the geological record.  Based on this record, we can expect several times as much warming as we have experienced since 1750.  Most of this lag effect will come from (1) changing how much sunlight Earth reflects (much less snow and ice, loss of sulfates (from burning coal), and less cloud cover), plus (2) further carbon emissions from thawing permafrost (and methane hydrates and soils), and (3) more water vapor (a key greenhouse gas) in warmer air.  A bit will come from (4) slowly heating up the oceans until Earth’s energy in = energy out.  (Oceans already gain almost as much energy per year as all the energy humans have ever used.) 

     The last 2 times we had this much CO2 in the air (about 4 and 14 million years ago), global surface temperatures were 7 and 10°F warmer than now and seas were 65-130 feet higher.  We can expect today’s 400 ppm of CO2 to have that effect again.  Lag effects of today’s carbon dioxide (CO2) & methane (CH4), much of it from compounding albedo changes when half of Earth's ice vanishes, are very large.  They can make summer highs in Kansas, Oklahoma, and Texas - even South Carolina, Georgia and Idaho - hotter than those in Las Vegas now - by 2100 if the pace over the last 20 years continues.

   For at least half the last 600 MY, Earth's surface been 15-30°F warmer than now, with CO2 levels at least 5 times today's, much higher till 350 MY ago.

     Starting ~ 375 MY ago, CO2 levels fell steeply, after plants colonized land.  Glaciers were widespread ~300 MY ago.
     Oxygen levels generally fell when CO
2 levels rose, and vice versa.  That’s true over the past century, too.

    In part, higher CO2 levels compensated for a dimmer sun in the distant past.  Our sun brightens slowly as it ages, warming Earth about 2°C more per 100 million years.

           Our sun also brightens, then dims, by ~ (about) 0.1% (from minimum to maximum), during "11-year" sunspot cycles (usually 10 to 12 years).  2008 saw the fewest sunspots in 111 years, so it’s no surprise that solar radiation was the lowest in the 40-year satellite era.  Variation during longer (more variable in length) sunspot cycles is subtler.  Solar changes do influence climate.

     In the satellite era, Earth warmed as the sun brightened, and cooled as it dimmed, mostly - until 2002.  Solar variability's influence on climate is now modest.  During 2002-2008 and 2014-16, Earth’s surface temperature rose while solar output fell.

     CO2 levels have varied a lot over the eons (see above for 570 million years).  Very long ago (~250 MY, etc.), vast lava eruptions lasting a million years or so, such as the ones that created the Siberian Traps and India's Deccan Traps, and even the Columbia River Basalts, added lots of CO2 to the air: multiples of what we have now, over thousands to millions of years.  Current (e.g., 20th century) volcanic eruptions add more modest amounts: roughly 1% of current human CO2 emissions.

     When continents collided, mountain ranges rose.  As moist air moved over them, they caught more rain and snow.  This speeded up rock weathering processes, which annually remove 3% as much CO2 from the air as humans now put in.  In weathering, CO2 dissolved in water combines chemically with minerals (mostly calcium silicates) in rock surfaces, which wash away to become sediments.  This has been so for hundreds of MY.

     During the PETM temperature spike 55 million years ago, global temperatures rose by 0.025 to 0.06°C per century.  For comparison, surface warming over the past century was 1.2°C. This has speeded up.  Over the past 20 years, the warming rate was 2.3°C per century.   

     Weathering in the Himalayas has driven COlevels down for some 50 MY, from some 3 times current levels (see 1st figure above).  Ebbing CO2 enabled glaciation in Antarctica starting 34 MY ago.  As CO2 ebbed further, Greenland glaciation began 18 MY ago and hit its stride 8 MY ago.  Finally, as CO2 levels fell further, widespread glaciation began in Canada, Alaska, Scandinavia, most of Siberia and the northern US ~ 2.5 MY ago (punctuated by interglacials).  Note how glaciers ebbed in Antarctica from 27 to 13 MY ago, as temperatures rebounded by 1 to 2°C for 14 MY.
     Algae, plants, and seashells also remove CO
2 from the air, to store in soil or water, once life took hold.  When life spread to land, the process speeded up (see above).  As conditions permitted, these dead lifeforms made coal, oil, gas, and limestone, which stored carbon underground.  This has also been going on for several hundred MY.

      During ice ages over the past 2 MY, CO2  & CH4 levels were much lower than today's (~ 400 parts per million [ppm] of CO2 in the air).

     The timing of these ice ages (once general CO2 levels dwindled enough - credit the Himalayas & an isolated continent at one pole), was driven by Milankovich cycles - small variations in Earth's tilt, the roundness of its orbit, & when it's closest to our sun (in northern summer, winter, or in between).  The "beat", when these rhythms reinforce each other, comes about every 100,000 years.

     Finer time resolution for these ice ages shows warming came 1st, followed "shortly" by more CO2 and CH4 in the air.  It seems that warming, from natural orbital factors, drove carbon out of permafrost (CO2 where it's dry, CH4 where it's wet), oceans, and soils.  Warming speeds up decay by soil microbes.

     Worldwide warming averaged .04°C per century from 20,000 to 10,000 years ago, but twice that at Vostok.

     The relationship of CO2 (and CH4) to temperature about 4 and 14 million years ago is essentially the same as shown in the more recent Vostok ice cores.  See graph below.


     The green line connects the patterns relating temperature change to changes in CO2 and CH4, over the last few ice ages, to those the last times we had about this much CO2 and CH4 in the air.  The story is consistent across millions of years.  The equation shown in green has the best explanatory power (R2).  The natural logarithm  (LN) adjusts for GHG moelcules getting in each other’s way as they become more numerous, so that a smaller fraction of them actually absorb outbound infrared radiation over a given timespan.

      With current CO2 & CH4 levels, the equation yields global warming of 7.8°C.

     The purple line connects the patterns relating temperature change to changes in CO2 only.  Neglecting CH4 provides an appreciably worse fit to the ice core data.  It implies just 4.5°C warming from today’s CO2 levels.

     (Since 1750, CH4 levels have risen far faster than CO2 levels, 163% vs 45%, especially in the 19th and early 20th centuries.)

     What’s going on?  Over a few decades, Arctic sea ice will vanish, as will sulfates from coal power plant smokestacks.  Over many decades, snow cover keeps shrinking, arriving later and especially leaving earlier.  All these changes make Earth darker, so it absorbs more heat.
     More important, over the past 30 years, Earth’s cloud cover has probably been decreasing by .064% per year.  That makes Earth darker, so it absorbs more heat.  This is actually a very large number, since Earth is large and half covered in clouds.  The effect of the observed cloud cover decrease (in 2013 AMO report) is about half as much over 30 years as the warming effect to date from all greenhouse gases.
     That’s assuming the ratio of high-altitude clouds to low-altitude ones stayed roughly the same.  However, since 2001, high altitude (warming) clouds have increased.  Since 1983, low altitude (cooling) clouds have decreased, while middle altitude clouds have increased.  (See Heat page, Clouds section.)  Finally, low clouds have been growing more opaque (Clouds section); this partly offsets the shrinking area and the growing high-to-low cloud altiude effects.  The overall cloud effect, a fast feedback, is a multiplier; it adds 19% to warming from other factors.

     In addition, smaller albedo changes come over many decades to a few centuries, as ice vanishes from almost all of Greenland and West Antarctica.  (In recent years (to 2012), ice loss accelerated 12% per year in Greenland and 19% a year in Antarctica.)  Earth’s surface continues darkening.  Thus, Earth absorbs still more more sunshine, heating up more.  This creates a positive feedback loop.  Most of the heat absorbed goes into the oceans, but a small fraction heats the air, another melts ice, and another heats soil and rock.

     All these albedo changes will be multiplied by more water vapor in the air.  Water is a greenhouse gas.  It amplifies warming from other causes: other greenhouse gases and albedo changes.  Air holds 7% more water, at the same relative humidity, for each 1° warming.  The difference between relative humidity and absolute humidity is quite important: more water vapor in warmer air does not mean more clouds.  The 7% more water vapor increases the heat effect (“radiative forcing”) by 1.5 Watts / square meter, about 2/3 as much as all other factors combined, or another 0.6-0.7°C water vapor feedback for 1°C warming.

     This amplifies the direct effect of CO2, CH4 and other greenhouse gases - a lot.
But it also amplifies the effects of albedo changes.

  4.5°C global warming is plenty to make Kansas as hot as Arizona.
7.8°C make Kansas hotter than the Sahara.

     Earth has natural cycles that last for years.  El Niño / La Niña is the most prominent of these.

     Elevated CO2 levels have long been used in greenhouses to increase production of flowers and vegetables.  This uses the "CO2 fertilization effect", boosting yields by 6-35%.  However, plant growth is limited by many factors - temperatures too hot or cold (e.g., below freezing), low light levels (night, etc.), CO2, water, nitrogen, phosphorus, potassium, acidity, soil depth, etc.  When CO2 is a limiting factor, adding more CO2 helps plants grow, especially C3 plants - until the plants run low on another factor, usually nitrogen.  This explains why experiments find that an initial (1-5 year) CO2 growth spurt fades.  C3 plants include most food crops (but corn and sugar are C4) and weeds.

Human-Accelerated Climate Change

     Especially in the past century, humans have added lots of CO
2 to the air - by burning coal, then oil, then also natural gas.  Cutting down forests and farming practices (tilling, feedlots, rice paddies, etc.) are other factors.

     These can, and do, speed up natural climate change.
     The last time CO
2 levels were this high, Earth’s surface temperature was about 7°F warmer. 

        After a Medieval Optimum and 3 Little Ice Ages (see Heat page), land surfaces warmed from 1890 to 1942, plateaued to 1974, warmed steeply to 2004, little till 2012, then shot up again.
     Sea surfaces warmed 1/4 slower than land surfaces.

    Q: If COcauses warming, why doesn't warming increase as smoothly as CO2?
    A: Sulfates.  See below.

     Note that global land surface temperatures are ALREADY 1.6°C above 1880 (5-yr moving average), according to NASA (1.8°C says NOAA).  They are very likely more than 1.5°C above the 1750 level, a target in the December 2015 Paris Accords.  And they are not headed down.

     However, sea surfaces have warmed more slowly.

.    Earth's land surface has warmed about 1.5°C (2.7°F) since 1917. That includes 2.4°C (4.2°F) per century since 1967 and 2.6°C (4.7°F) since 1997 .  Warming since 1917 has been 70 times as fast as it was 11,000 to 7,000 year ago, or ~35 times as fast as from 18,000 to 11,000 years ago.  And still faster in more recent years.  Earth’s surface has been warming far faster than before humans put lots of CO2 in the air.

     93% of Earth's heat gain went to warm the oceans (including 80% to only 700 meters deep), while only 2% went to warm the air - which is mostly the warming we care about.  The rest melted ice, heats rock & soil, and increased water vapor in the air.  Over the past decade, the % that heats the ocean has risen (due to more vertical mixing and much more heating in the ocean below 700 meters), while the % that heats the air has fallen.

     The rate of ocean heat gain has accelerated, especially since 2005.  Since 2005, oceans added heat 25 times as fast as humans now use energy (~150 x as fast as the US does).

    Since 1969, ocean heat gain exceeds 10 x the energy humans have 
ever used: ~ 3,000 years of current US energy use.  The tail is wagging the dog.  (Humans are wagging Earth's oceans and air).

    However, heat temperature.  Heat = temperature x mass x heat capacity per mass.  Since the oceans weigh 260 times as much as our air (& water has 4 x the heat capacity of air), air* has warmed much faster than oceans.  This is slightly so at the sea surface, but dramatically so for the deep ocean, which is warming slowly.
The troposphere, where most of Earth’s air is located, is the part of the air that is warming.  The stratosphere is cooling.
     For heat to seep down from the sea surface to the deep ocean takes a long time.  If CO2 levels in the air levelled off, the deep ocean would continue to warm slowly, until a new thermal stratification equilibrium is achieved.  In 2011, it was estimated that such a new equilibrium would eventually warm the sea, and sea surface, another 0.6°C.  It takes roughly 1,000 years for the global thermohaline circulation, driven by formation of deep water off Greenland and Antarctica, to make one circuit.  This is a rough estimate of the time it takes to warm another 0.6°C in response to TODAY’s greenhouse gas levels.

     Air temperature WAS warming 50 times as fast as the ocean, but is NOW warming only 25 times as fast.  Heat has been seeping faster into the deeper ocean. So, we saw a 2004-12 slowdown in warming AIR across the world.

     Global warming actually accelerated since 2005.  The 2004-12 ‘hiatus’ (which ended) was confined to the air, NOT the ocean.  That air “hiatus” has reversed, in spades.

     The graph above shows much of why air has not warmed as smoothly as CO2 levels rose.

Moving averages include 2017 to date, where appropriate.

     Effects of sulfates are clear for major volcanoes, which put sulfates in the stratosphere for many months. (Smaller eruptions - too many to show - had much smaller effects.)
    The bigger picture (numbers 40-118 in bottom box of the Temperature / Sulfates slide, near the bottom of the “Heat” webpage) is that, over 135 years, human sulfur emissions mostly rose, especially 1940-60, to peaks in 1973 and 1979.  That masked much warming from CO2.  But when sulfate levels fell (1930s, 1975-2005), warming was unmasked.  Then temperatures rose steeply.

∆°F 26 US Places 75-15

     One result of added CO2 has been warming in America.  Since 1975, daily summer highs in 26 places* around the US have increased, on average, by 3°C (5.4°F / century), a bit faster than Earth's land surface as a whole.  From 1975 to 1995, the 26 barely warmed.  (Jointly, the 40-year urban heat island effects shrank (cooled) for these 26 places.)  
     But since 1995, they've warmed 10°F / century.  The summers of 2011 and 2012 were especially hot.  Maybe it's just year-to-year variability.  Maybe it it's more than that.  But if warming continues as fast as it did from 1995 to 2015, by 2100 
summers in Kansas and Oklahoma, Georgia and South Carolina would be hotter than Las Vegas ones now.  That’s bad for crops.  Summers would be still hotter in Texas.

     Still, 26 is a small sample and 20 years is not so long.  So, error bars on extrapolation are substantial.

     With a larger sample of 330 places, the picture is very similar.  See the Heat page for regional graphs and the Data page for individual city graphs and data.  The results are similar, but the warming is a little faster (+5.8 and +10.5°F / century).
     Warming varies a lot from one region to another.  It’s been fastest in drier areas: Rocky Mountain and West South Central states.  Warming was also fast in South Atlantic states - except Florida.  Warming was slowest in North Central states and Alaska.

     Why was warming fastest in the Rockies and West South Central states?  Here’s an idea:

     On land, sunlight absorbed evaporates water, if available; otherwise it mostly heats air.  At sea, it also heats water below the surface.  Preliminary research on US daily winter lows and daily summer lows shows only weak and ambiguous trends, lending further support to this hypothesis. 


     How long until summer highs average as hot as Las Vegas ones todayIF recent trends continue?

     1995-2015 trends, especially in the faster warming areas, are truly sobering.
     If these 20-year rates (which vary by place) should continue, today’s Las Vegas summer heat comes to Fresno in 2036 & Austin in 2037.
     At the state average level, 
Nevada, Texas and Arizona summer heat would be as severe by 2080.  Idaho, South Carolina, Kansas ("breadbasket of the world”), Oklahoma and Georgia would grow as hot shortly before 2100.

     Alabama, Colorado, Utah, Louisiana, and North Carolina would join them early next century.  Wyoming, Tennessee, Mississippi, Virginia, New Mexico, Montana and West Virginia would also join them by mid-century.  Other states would grow that hot later.

     Humid areas - such as Georgia, South Carolina and Alabama - could become uninhabitable during summers late this century.

Slowing and even stopping such warming is utterly important.

     Daily low temperatures, summer and winter, have not risen much or have even fallen (winter lows, 2nd half of 42 years).  But summer highs have risen fast.  Evaporation is higher then and soil moisture levels can be lower.  See Heat page for more summary of summerand winter lows and the bottom of the Data page for details on them.

     Oddly enough, since 1994, when (in any single year) Earth's land surface warmed faster than its trend, the US usually warmed slower than its trend, and vice-versa.  (Correlation = -0.39.)  Food for thought.

     2012's summer heat could become the new normal within the lifetimes of most of us, by 2030 in several states.
     In the longer term, unless carbon emission rates are cut sharply, by 2200 a few areas (e.g. Persian Gulf) could become too hot and humid for humans to survive in.  Even Alabama, Georgia, and South Carolina sometimes in the summer.  If CO2 levels reach 650 ppm and CH4 evels rise similarly, by 2300, large sections of Earth (e.g. most of Australia, India, the 
eastern US) could become too hot and humid for humans to survive.

     If CO2 emissions are a major cause, to slow down heating or even stop it, we must do 3 things.

     1. Stop burning money (use energy efficiently), whether or not CO2 is a problem.
 2. Use low- & no-carbon energy (more wind - cheaper in some areas - sun, etc.; natural gas for 1-3 decades; for at least a few decades - nukes).  Use less coal (and oil).  Long term, phase out gas, then maybe nukes.  If we burn all fossil fuels in the ground, Earth would become ice-free and seas would be more than 200 feet higher.  Much of Earth would be too hot for humans to survive.
 3. Take carbon out of the air faster than we put it in.  Pay ranchers & farmers to put it back in soils, etc.

     Warming has consequences.  Perhaps the most important is faster evaporation, which helps bring intense droughts more often.  (Between droughts, we get worsening floods.)  Here is a projection from 1989, in 2 forms.  Larger views appear on the Overviews page and in the middle of the slide show (available below).

Now, change from looking forward to looking backward: the world below left, the US below right.

Droughts HAVE, in fact, been increasing.
See graphs at left and below.   .

Observation up to 2002 matches projections made in 1989.  Worldwide, severe droughts have been increasing.

Growing droughts are bad for our food supply.

     World grain production per acre plateaued  (bottom line in table at left) from 2008 to 2012, but rose 8% in 2013-14, due mostly to record US yields.  Still, humans added more people and fed more animals for meat.

     So food prices rose (see below, also Food page).

     Current agricultural models estimate that climate change will directly reduce production of corn and wheat (and with yet more warming, rice, and eventually soybeans too).  These 4 supply 80% of human calories.  Tropics suffer first, temperate zones later (with overlap).  One model estimates a reduction up to 43% by 2100, another more.  The IPCC now estimates 17%.  With shrinking fresh water supplies, especially dwindling groundwater, further large declines loom, absent big improvements in water use efficiency.  Pressure on food supplies is not likely to stop after 2100.

Less food feeds fewer people.

Reducing Earth's population to fit the future food supply will not be pretty.
Think Bosnia, Rwanda, Darfur, Somalia.  Boko Haram, ISIS.  Multiply.

     Some aspects of climate change we know much better than others.
Perhaps the greatest uncertainties are for

1. how much and how fast we can move CO2 from ambient air to carbon sinks;
2. future carbon escape rates from 
permafrost and methane hydrates;
3. large scale changes in % 
cloud cover;
4. future carbon escape rates from other soils; 
5. future human carbon 
6. future effects on the food supply;
7. future rates of 
sea level rise (Antarctic & Greenland melting);
8. how much future warming is unmasked, as we stop emitting sulfur (with CO
9. loss rate for sea ice;
10. effects at
regional (e.g., Australia) and sub-regional (e.g. Britain) levels.

     Below is one take on how the future will unfold, to 2400.  In the Base Case, CO2 & CH4 emissions peak ~2012.  It includes many albedo (reflection) effects: reduced cloud cover, sulfates, ice and snow.  It also includes strong effects by carbon emissions from permafrost and methane hydrates.  It underestimates carbon loss rates from other soils and from de-gassing from the oceans.
     The overall results are highly 
consistent with the warming equations derived from the Vostok ice cores.  Especially ∆°C at Vostok = -107 + 19.1 * LN (ppm CO2).  Moreover, using today’s very high methane (CH4) levels would make the picture appreciably worse than shown just below.

     Permafrost emissions are from MacDougall (see Overviews page).  They correspond to DEP 6.0 in the Base Case, 4.5 in the case where fossil fuels are eliminated by 2050, and 2.6 in the case that also includes very large-scale carbon capture and sequestration - from ambient air.  Higher DEP cases (than 2.6 emissions in Dr. Fry's Base Case) are used in Dr. Fry’s modeling above, to compensate for demise of cooling from sulfates and Arctic sea ice, plus cooling from fewer clouds observed in recent years (see Heat page, Clouds section), all of which were not part of MacDougall’s model.  Systematic changes in cloud cover are subtle.  See “Clouds” on the “Heat” webpage for details.

     McDougall is conservative in several other ways: 1) his estimate of the permafrost carbon pool is only 54% of more recent estimates, 2) he does not include methane hydrates (which recently emitted 30% as much carbon per year as permafrost), 3) he does not account for CH4 release from permafrost, 4) he does not account for thermokarst and water erosion of permafrost, 5) he does not account for permafrost warming by black soot from increasing near-Arctic forest fires, and 6) his temperature estimates for the permafrost region are at the low end of the range for the literature.

     Future temperature changes will likely be dominated by permafrost carbon, diminishing cloud cover, and increasing water vapor.  Well before 2100, elimination of sulfates (a coal by-product that increases cloud cover) and Arctic sea ice play substantial roles.  (See future temperature graph above from 2010 to 2070.)  They both induce positive feedbacks from permafrost and clouds.  Shrinking ice and snow cover play smaller but similar roles, over a few centuries.  Looming above all is the water vapor warming amplification effect.

     Future ice loss rates from Greenland and Antarctica are uncertain.  But several new ice dynamics processes have been identified that were not in earlier models.  All of them speed up ice loss projections.  So, for example, DeConto and Pollard (2016) cut their estimated melt times for much of Antarctica from a few million years (2013) to a few hundred (2016).  Sea level rise shown here to 2100 is half that projected by Hansen et al. (2016), and to 2400 is similar to DeConto and Pollard (2016).

     The general temperature increase is very consistent with Snyder (2016, see Overviews page for summary). Also based on more detailed paleoclimate data than used in the graphs above, Snyder foresees 5°C eventually from today’s CO2 levels and 9°C with 560 pm CO2 (double pre-industrial).  But she does not envision the warming to happen this quickly as I do; short-run warming of about 3°C.

     This all points to the utter importance of removing from the ambient air most of the carbon humans have put in it by burning fossil fuels.  The sooner the better, much of it this century.  It would be good to go carbon negative as a species before 2050.  Civilization cannot survive the temperatures indicated if we fail to do so.  The world food supply would be cut in half at 5°C global warming.  9°C warming would be far worse.  Past major extinctions have been driven by large climate changes due to copious CO2 emissions.


     Some people are looking into ways to remove carbon from the air and store it in soils, rocks, trees, or oceans.  Carbon removal is a major topic on the page "Carbon + & -".  Others are looking at ways to block sunlight from reaching Earth's surface, a geo-engineering topic discussed on the “Tons, PPM, $" page.  Blocking sunlight will not help with ocean acidification, but enough carbon removal will.
     In 2013-14, China began CO2 cap & trade in 7 large emitting places. It plans a nation-wide system in late 2017.  China’s coal use fell starting in 2013.  As a result, world CO2 emissions levelled off in 2014.  China's peaked in 2012.  China’s CO2 emissions fell even faster (5%) in 2015.  Again, world CO2 emissions did not rise.
     Meanwhile, on June 1, 2015, 6 major oil companies called for a worldwide carbon price.  They already use internal “shadow” prices such as $40 or $34 per ton of CO
2.  In the run-up to the December 2015 Paris climate summit, 32 renowned economists, including 4 Nobel Prize winners, called for a worldwide carbon tax.

     Again, we can all (1) use energy more efficiently, saving money in the process.  Many of us can also (2) use green energy.  This creates many more American jobs than using fossil fuels does.  It cuts our dependence on foreign oil (and tames our foreign debt).  Some of us can (3) remove carbon from the air with grazing and tilling practices on farms, ranches, and gardens.
     The good news is that China’s coal use peaked in 2012.  Chinese officials had been talking about a peak soon, as had financial analysts.  China is cutting coal use most of all because its air is so terribly polluted, hard to breathe, taking 5-6 years off a typical Chinese life.
     Moreover, in 2016, the US is emitting CO
2 at the slowest rate since 1987.  2% lower still in 2017 so far.    In many places, India’s air is even more polluted than China's.  India has begun to follow in China’s footsteps.  It  is leveling off its coal use and canceled most proposed coal plants.  As solar gets even cheaper, cooling water shortges lead to more thermal power plant shutdowns at inopportune times, and richer Indians do not want their lives cut short by 3-7 years.  So, India is expanding its renewable electricity production exponentially and will end petroleum vehicle sales by 2030.

Slide Shows & Library

     A CD version - April 15, 2016 edition - can be downloaded here.  It contains several slide show versions (as below, but at a snapshot in time), 1,000s of articles, a few books, and some miscellaneous documents.

     The main presentation summarizes global warming - the evidence, the impacts, and what to do.  It is available in PPT and PPTX formats:
Global Warming - So What? PPTX (Office 2011)

     This set of 87 slides  takes 75 minutes to view.  Many of the slides are dense with information, so information on slides generally rolls out a bit at a time.  When a black dot appears in the upper right corner of a slide, click to continue.
The slides works well with PowerPoint, but the many graphs, plus timing and direction of text roll-out, get mangled with Keynote.  Open Office is also missing text color.)  If you cannot use PowerPoint, try the PDF version, available here:
Global Warming - So What? PDF.

Global Warming - So What? PPT (older Office), with 83 slides is also available.  It was last updated in April 2017.

      Much of the same information is here (Global Warming - So What - DOC), a scholarly paper with references.  It is an abridged version of the slide show, with less detail than the Lite version but more than the Mini one.

    Additional slides, with further details, are available here in PDF format: Additional Slides.  These 34 slides take almost half an hour to view.

     Shorter slide shows summarizing the situation are also available.
They have most, much, or some of the same information.

     Global Warming - So What? - Lite (PPTX) has 71 slides.  It takes 60 minutes to view.  It omits many details.

The PDF version is here: Global Warming - So What? - Lite PDF.

The older PPT version is here: Global Warming - So What? - Lite.

  Global Warming - So What? - Mini (PPTX) has 57 slides and takes 45 minutes.  It also omits explanations of warming.
When a recent version of Office (PPTX) opens an older version (PPT) file, it declares an “error.”  Formatting changes it makes to “repair” the file create a few vertical mis-spacings in complex text.)

  Global Warming - So What? - Micro (PPTX) has 39 slides and takes 30 minutes.  It also omits solutions, except CO2 removal.  It was last updated in December 2015.

  Global Warming - So What? Audio This hour-long talk is a version from 2007, updated in 2012.

       The presentation below focuses on lessons that climate change in earlier eras holds for Earth’s climate in the next few decades to centuries.  Written for scientists, its 35 slides take 24 minutes to view.
4.5 to 7.8°C Global Surface Warming from Today’s CO2 and CH4 Levels

       The presentation below focuses on lessons that climate change in earlier eras holds for Earth’s climate in the next few decades to centuries.  Written for a broader auduence, its 31 slides take 20 minutes to view.

320 ppm - Why Humanity Must Move Far Beyond Carbon Neutral

     The 26-slide presentation below gives more detail on temperature trends in the US.  It takes 13 minutes, plus appendices (54 slides) with details for each region and state. US City Summers Are Warming 10.5°F / Century

     17 more web pages address aspects of climate change.  They include excerpts from the slide shows, plus many other graphs, maps, tables, diagrams, and explanatory text.  5 pages show how climate is changing, starting with Overviews.  5 pages detail impacts, starting with Food.  3 pages cover energy, starting with "Coal, Oil, Gas, Nuke”.  2 pages cover emissions, pricing, CO2 levels, politics of warming, investment, and so forth.

     These pages contain several books, plus almost 9,000 articles, with 800-1,600 illustrations (some multiple panel, some duplicate), most drawn from the articles.  Most pages have 6-18 sections, each with 6 to 150 articles (files) and usually some illustrations.  (Over 1/2 of the 8,000+ articles appear in more than one place, as relevant.)  Links to other sections on a page appear above and below the sections.  Links to other pages appear atop each page.

     Some 350 articles in PDF form are original scientific studies or summary studies (e.g., IPCC report pieces or US National Climate Assessment chapters).  But over 8,000 are summaries of more studies (RTF format, plus a few in DOC), drawn from the scientific press.  About 500 more files are small data bases in XLS (e.g., daily Arctic Ocean ice area; weekly US drought indices; monthly US electricity by source / fuel; annual CO2 emissions by nation; mean of daily summer highs, by US city by month and year; etc).

Dr. Gene R. H. Fry

by Gene Fry 2017