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Global Warming – So What?
Gene R. H. Fry
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Abstract - Since 1880, Earth’s surface has warmed the fastest in many millions of years. Oceans now gain more energy per 2 years than cumulative human energy use. Since 1993, the US warmed very fast: 1.2°F / decade. That pace turns Kansas, “breadbasket of the world,”into desert by 2100, while 2012 US heat becomes its new normal in 2020. Sulfate level variations explain temperature deviations from a smooth CO2-induced trend.
Current CO2 levels entail large lag effects: ~1.7°C, on top of 1.04°C (land) since 1913: 0.5-0.6°C each from Arctic Ocean albedo changes, phasing out coal’s sulfur emissions (both complete by 2100), and warming Earth enough so outgoing radiation equals its heat gain. This CO2 level-temperature relation is supported by multiple paleoclimate studies. Carbon emissions from permafrost can increase warming more, even absent further human CO2emissions.
In 1990, Rind et al. projected that, warmed 4.2°C by CO2 double 1750 levels, Earth’s “1/century” drought frequency would rise to 45% by 2059. This results in savannas, prairies and deserts replacing forests; 70% lower biological net primary productivity; and 30-50% losses in America’s major food crops. In 2004, Dai et al. found that actual 1950-2002 severe drought frequency matched Rind’s projections.
Farmers have staved off crop declines by mining groundwater, notably in north China, north India, central California and the Great Plains. Most major wheat producers (plus the Amazon, twice, among others) have suffered 1/century droughts in the past decade. Grain yields per hectare have plateaued worldwide since 2008. Several studies found that warming cut crop yields, such as 10%/°C warming. One warned of 37-82% crop losses by 2100, due to heat spikes. Doubled world food commodity prices from 2007 to 2011 led to food riots and toppled governments.
The world may lose of up to half its food supply, perhaps by 2100, featuring water wars. Human population could fall steeply, threatening civilization’s collapse. But other species would fare worse. A study estimated the present value of projected warming damages exceeds gross world product, cutting GWP by 3%/year.
It is vital not only to reduce CO2 emissions to zero (many methods are reviewed), but go carbon-negative in a big way. Major ways to move carbon from air to soils or elsewhere include fast-rotation grazing, organic (and no-till) farming, accelerated rock weathering, and farming the ocean.
Index Terms—US warming, droughts, food supply, bio-CCS.
I. INTRODUCTION
This review emphasizes impacts from and solutions to rapid warming. Bottom line: we should pay ranchers and farmers to move carbon from the air back into soils.
Why? We alreadyhave too much CO2 in the air. Warming (since 1880) could well triple, even without more CO2. Blame vanishing Arctic sea ice (0.5-0.6°Cmore warming), phasing out coal’s sulfur emissions (similar), and warming Earth enough so energy out = energy in (similar). Moreover, carbon in permafrost could increase atmospheric CO2 levels by 100 ppm or more, even without further human carbon inputs.
Manuscript received June 6,2014. Gene R. H. Fry is retired. (phone 781-698-7176; e-mail . website
Water
Rainfall becomes more variable. Planet-wide, we get a little
more rain. Around the Arctic gets lots more, but mid-latitudes (20-40°) mostly get less than now. Yet in any one place, we get more hours and days without rain [1]. That is, we get more downpours and floods, yet also longer, drier, hotter droughts.
II. THE TEMPERATURE RECORD
Recent US Warming
US daily high temperatures, June 1 thru September 30, rose steeply over 1978-2012, especially over 1993-2012 - for26 cities with declining urban heat islands, scattered around the US.[1] Results are very similar for 81 moreUS cities, not shown.
Figure 1. USMean High Temperatures, June 1 – Sept. 30
Consider Salina, Kansas, in the heart of wheat country, breadbasket of the world. Warming at 3.3°C [5.9°F] / century, by 2100 summer in Salina would be as hot as Dallas now. At 7.0°C [12.6°F] / century, by 2100 it would be as hot as summer now in Las Vegas, where no crops grow.
Warming at the 107-city, 1993-2013, 6.7°C rate (faster in central states), 2012 US heat becomes itsnewnormal in 2020.
CO2 Levels: Now and Then
The CO2 level in Earth's atmosphere is now 400 ppm. That is up 43% since 1750 and 36% since 1880, when NASA temperature records began. In 1915, CO2 passed the 300 ppm maximum between the last several ice ages.
400 ppm was last exceeded 15 million years ago [2]. 15-20 million years ago, Earth was 3-6°C warmer than now and seas were 25-40 meters higher [2]. CO2 levels were as high as now 3.0-3.5 million years ago [3], [4]. Earth then was 2-3°C warmer and seas were 20-35 meters higher[3], [4].This means ice then was gone from almost all of Greenland, most of West Antarctica, and some of East Antarctica.
CO2 levels now will likely warm Earth’s land surface ~2.7°C, not just the 1.0°C seen to date. We face lag effects. Current CO2 levels are already too high for us. So far, half the CO2 we have emitted has stayed in the air [5]. The rest has gone into carbon sinks - into oceans, soils, trees, rocks. This natural sequestration could shrink, even reverse.
Ocean Heat Gain
Of the net energy absorbed by Earth from the Sun, ~84% went to heat the oceans [6]. 7% melted ice, 5% heated soil, rocks and trees, while 4% heated the air [6]. Since 2007, ocean heat gain has switched to 70% below 700 meters deep [7]. Moreover, now 90% goes to heat oceans, while less heats air, rock, and ice [7]. We notice air heating slower. Warming is sensitive to the partition of heat gain between water and air.
Figure 2. Ocean Heat Gain [9]
Yearly ocean heat gain from 1967 to 1990 was 40 times US yearly energy use [8], [9].From 1991 to 2005, it was 70 times as much. Since 2005, it has been 120 times as much. Ocean heat gain since 1967 equals 3,000 years of US energy use.
Sulfate Cooling Effects
Figure 3. Sulfates Affect Surface Temperatures
The temperature baseline is 1951-80.Short-term (1-4 year) effects of major volcanic eruptions are clear. So are2-decadetrends, most up, some down, from sulfur emissions by smokestacks(ppm numbers in rectangle near bottom [10]). The IPCC estimated sulfates offset 30-40% of warming from greenhouse gases [11], [12]. Abolishing them will warm Earth.
Earth Is Heating Up
Earth now absorbs0.25% more energy than it emits: a 300 (±75) million MW heat gain [13]. 300 million MW = 70 x world electric supply = 20 x human energy use. Absorption has been accelerating, from near zero in 1960. Earth will warm another 0.6°C, so far, just so it emits enough heat to balance absorption [14].
Air at the land surface is 1.04°C warmer than a century ago. Half that warming happened in the last 33 years. Air at the sea surface is 0.8°C warmer than a century ago [15]. As Fig. 2 shows, the oceans have gained ~ 10 x more heat in 40 years than cumulative human energy use.
III. IMPACTS – ICE, WATER, DROUGHT
Reservoirs in the Sky
Most mountain glaciers are shrinking ever faster - in the Alps, Andes, Rockies, and the east and central Himalayas [16]. 30% of Himalayan glacier ice vanished since 1980 [17]. When Himalayan glaciers vanish, so could the Ganges River (and others) in the dry season.
Mountain snows melt earlier, so California’s San Joaquin River (Central Valley, US “salad bowl”) could dry up by July in most years; in 2013 it again dried up much earlier [18].The Colorado River’s recent 10-year drought was the worst since white men came [19].
Permafrost
Permafrost’s releaseof methane (CH4) in wet areas, and CO2 in dry ones,revs up warming in a vicious circle. Thawing Arctic permafrost holds 6 x the carbon ever emitted by our fossil fuels = 2 x the carbon in Earth’s atmosphere [20]. Permafrost area shrank 7% from 1900 to 2000 [21]. It may shrink 75% more by 2100 [22].
Already, permafrost carbon emissions approximate those from US vehicles [23]. Thawing permafrost can add up to ~100 ppm of CO2 to the air by 2100, and ~300 ppm more by 2300, for up to 1.7°C more warming [24]. Seabed methane hydrates and Antarctic permafrost hold much more carbon. We may repeat the 6°C PETM warming 55 million years ago [25].
Polar Ice: Albedo and Sea Level
Arctic Ocean ice is shrinking fast. Minimum ice area fell 37% in 34 years[26], while volume fell 72%, 53% in the last 10 years [27]. The ice got thinner too!The bright ice could melt away by fall in 3-7 years and be gone all summer in 7-20 [27]. The dark water absorbs far more heat than bright ice. As ice recedes, Earth absorbs more heat; it will warm more, even without more CO2: so far, like 20 extra years of CO2 [28].
Greenland’s net ice-melt rate rose 5 x in the past 15 years [29].So, the ice cap’s simple life expectancy fell from 60 millennia to 11. Its annual net melt-water is already 1/2 of US water use [30]. Antarctica’s yearly net ice-melt (West minus East) was ~ 1/3 of Greenland’s [29], but its melt rate doubled over 2007-11 [30]. It has 9 x the ice and will last longer.
Seas will likely rise 0.2 to 2 meters by 2100 [31] and30+ meters over centuries. Seas rose 1.5 meters / century from 13,000 to 6,000 BC [32]. This provides a starting-point estimate for coming sea level rise rates. Warming is far faster now, but only 1/3 as much ice is left to melt as in 13,000 BC.
Jet Stream, Drought, and Forest Fires
From 1979 to 2005, the tropics spread. Sub-tropic arid belts grew ~140 miles toward the poles, a century ahead of schedule [33]. That means our jet stream moves north more often [34]. In turn, the US gets hot weather more often.
2011-12 was America’s hottest on record. Over September 2011 - August 2012, relative to local norms, 33 states were drier than the wettest state (Washington) was wet [35]. In 2012, 44 of 48 states were drier than normal [35]. Severe drought covered a record 35-46% of the US, for 39 straight weeks [35]. Drought reduced the corn crop by 1/4. Record prices followed [36]. The soybean crop was also hit hard.
By 2003, forest fires burned 6 x as much area / year as before 1986 [37]-[39]. Pine bark beetles ravage western US forests [40]. Annual US forest area burned is expected to double again by 2050 [41].
Drought Frequency in Major Crop Producers
When I was young, the leading wheat producers were theUS Great Plains, Russia’s steppes, Canada, Australia, and Argentina’s Pampas. “1/century”droughts now happenthere once a decade.
Table 1. Recent Extreme Droughts
When / Where / How Bad2003 / W Europe / Record heat, 20-70,000 die. Hotter in 2012
2003-2010 / Australia / Worst in millennia. 100’s die. New record heat in 2013
2005 / Amazon Basin / Once / century. Worse in 2010, also bad in 2013-14 in Sao Paulo state
2007 / Atlanta, SE / Once / century
2007 / Balkans / Record heat, Greek fires, 100’s die.
2007-2009 / California / Record low rain in Los Angeles. All CA in extreme drought 2013-14
2008-9 / Argentina / Worst in half century
2008-2011 / north China / Tied for worst in 200 years. Severe drought in Yunnan ‘09-13.
2009 / India / Monsoon season driest since 1972
2010 / Russia / Record heat, forest fires,15,000 die. World wheat prices up 75%.
2011 / US: TX, OK / record heat & drought
2012 / US: SW, MW, SE / Most widespread in 78 years, record heat
Irrigation and Groundwater Loss
Over 1994-2007, deserts grew from 18 to 27% of China’s area [42]. Since 1985, half the lakes in Qinghai province vanished [43] and 92% in Hebei province [44] around Beijing, as water tables dropped below lake beds. Many wells in China’s wheat belt must go down 300+ meters for water [45].
Yearly net US groundwater withdrawals for irrigation grew since 1950, from 13 to 25% of US water use now [46]. So, the Ogallala Aquifer dwindles. 1/5 of wheat is irrigated in the US, 3/5 in India, and 4/5 in China[47]. Central California loses enough to irrigation yearly to fill Lake Erie in 100 years [48]. Groundwater loss from India’s Ganges Basin would fill Lake Erie in 10 [49]. With more evaporation andirrigation, many water tables fall 1-6 meters / year [50]. Worldwide, irrigation wells chase water ever deeper. Water prices rise.
Inland seas and lakes dry up and vanish, for example: the Aral Sea, Lake Chad, Lake Eyre, and the Sea of Galilee. More rivers fail to reach the sea more often: Yellow, Colorado, Indus, Murray-Darling, Rio Grande, etc.
IV. IMPACTS: FOOD
Droughts Set the Stage
As Figure 4 shows, NASA’s model projectedin 1990 that with “Business as Usual” emissions, CO2doubles (550 ppm) 1750 levels by 2059, causing 4.2°C warming and 14% more rain [51]. It projected droughts increase in severity and extent, so that “1/century” droughts cover 45% of Earth [51].
Extreme Drought Can Clobber Earth
Figure 4. Projected Drought Conditions in 2059 [51]
% in control run
Figure 5 shows the same projections as a time series. Over 2000-04, the average frequencies are 18% for “drought” and 33% for “dry”. A weighted average for “as dry as 11% of the time” drought is ~ 27%.
Figure 5. Projected Drought Conditions by Year [51]
In Figure 6, compare 30% actual severe drought area in 2002 (11% of the time during 1951-80) to 27% projected in 1990 (Figure 5)for 2000-2004. Droughts spread, as projected or faster. Earth’s area in severe drought has tripled since 1979. Evaporation worked its magic. Over 23 years, the area with severe drought grew by the size of North America. From 1979 to 2002, comparably wet soil areas shrank from 11% to 8% of Earth’s land area –by the size of India.
Figure 6. Historical Worldwide Drought Frequency [52]
US Climate Future This Century – UCS Study
In 2005-6, scientists calculated how climate would change for 9 Northeast [53] and 6 Great Lakes [54] states in 2 cases: (1) a transition away from fossil fuels, or (2) continued heavy reliance on them (business as usual emissions).
In 2085, averaged across 15 states, climate change would be like moving 530 km SSW (if coal and oil use shrink) or moving 1050 km SSW (if heavy use continues) [53], [54]. Consider central Kansas, heart of wheat country. 530 km SSW sits the area from Amarillo to Oklahoma City. 1050 km SSW is around Alpine and Del Rio, Texas,with <1 person / sq km. Cactus, mesquite and sagebrush grow there, but no wheat.
Droughts - Why Worry?
In 2059, with 2 x CO2 (Business as Usual emissions), Earth has more moisture in the air, but 15-27% less in the soil [51]. Average US streamflows decline 30%, despite 14% more rain [51]. Tree biomass in the eastern US falls by up to 40% [51]. More dry climate vegetation replaces forests: savannas, prairies, and deserts [51]. The vegetation changes mean biological net primary productivity falls 30-70% [51]. Switching from projections to actuals, satellites show that browning of the Earth began in 1994 [55].
Crop Yields Fall
NASA made 2059 projections for the United States, with doubled CO2 (Business as Usual emissions) in the Great Lakes, Southeast, and southern Great Plains regions - for corn, wheat, and soybeans. NASA’s GISS model projected (4.2°C warmer, 14% more rain) that crop yields would fall 30%, averaged across regions and crops [51].NOAA’s GFDL model projected (4.5°C warmer, 5% less rain) theywould fall 50%, averaged across regions and crops [51].
CO2 fertilization was not included [51]. So things will not be this bad, especially this soon. Temperature effects of doubled CO2 will keep growing, eventually to 4.2° or 4.5°C, but over many decades. CO2 fertilization (2 x CO2) boosts yields 4-34% in experiments [56], [57]where water and other nutrients are well supplied, and weeds and pests are controlled. That will not happen as well in many fields. Groundwater and snowmelt for irrigation grow scarcer in many areas. Other factors (most often nitrogen) soon kick in to limit growth, so CO2 fertilization will falter some.
Crop Data Analyses
As Table 2 shows, worldwide yields for cereal grains have leveled off. This is consistent with rising food prices, and with forecasts of falling crop yields. However, global population is expected to grow, leading to much less food per person.
For wheat, corn, andrice, photosynthesis in leaves slows above 35°C (95°F) and stops above 40°C (104°F) [58]. Warming (above 35° or 40°C) hurts warm, tropical areas harder and sooner [58].
Over 1992-2003, warming above the norm cut corn, rice, andsoybean yields by ~10%/°C [59]. Over 1982-98, warming in 618+ US counties cut corn andsoybean yields ~17%/°C [60]. With more CO2, 2°C warming cut yields 8-38% for irrigated wheat in India [61]. Warmer nights since 1979 cut rice yield growth 10%± in 6 Asian nations [62]. Warming since 1980 cut wheat yield growth 5.5%, corn 3.8% [63].
In Table 2 below, grains include wheat, corn, rice, barley, oats, rye, and sorghum. Million tonnes in 2011 are from FAO,yields from data.worldbank.org/indicator/AG.YLD.CREL.KG.
Table 2. World Cereal Grain Yields
Heat Spikes Devastate Crop Yields
Average yields for corn and soybeans could plummet 37-46% by 2100 with the slowest warming and 75-82% with quicker warming [64]. Why? Corn and soybean yields rise with warming up to 29-30°C, but fall more steeply with higher temperatures [64]. Heat spikes on individual days have big impacts [64].
More rain can lessen losses, since plants transpire more water to cool off. Growing other crops, or growing crops farther north, can help too.
Figure 7. Possible Changes in World Crop Yields, +3°C [65]
Figure 7 shows a possible future crop yield scenario. It is more pessimistic than the average among many studies. Like most projections, it does not include CO2 fertilization.
World Food Prices
Due in part to heat and drought stresses on crops, and with yields per hectare flat, the world food price index rose [65].Climate change probably played a role in that food situation.
Figure 8. World Food Price Index [66]
With food stocks at low levels, when food prices rose steeply in 2007-08 and again in 2010 (Figure 8), poor people could not afford to buy enough food. Malnutrition and starvation rose. Food riots toppled governments in 2011.
V. IMPACTS: SUMMARY AND COSTS
Projected Warming Effects by Degree [67][2]
2°C Warming - 450 ppm CO2e[3]
• Hurricane costs double. Many more major floods
• Major heat waves are common. Forest fires worsen.
• Droughts intensify. Deserts spread.
• Civil wars and border wars over water increase. [68]
• Crop yields rise nowhere, fall in the tropics.
• Greenland icecap collapse becomes irreversible.
• The ocean begins its invasion of Bangladesh.
3°C Warming - 550 ppm CO2e[4]