Future Climate Change

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Linda Cannon
5 years ago
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All predictions are based on global circulation models (GCMs,

1 Future Climate Change How do you know whether to trust a prediction about the future? All predictions are based on global circulation models (GCMs, AOGCMs) - model accuracy is verified by its ability to predict observed changes trustworthy untrustworthy 1

2 IPCC/UN asked modelers worldwide to use six emissions scenarios in their simulations The six SRES scenarios differ in 3 important ways: 2100 Population (billions) Energy Use (EJ/yr) % Carbonfree Energy CO 2 (ppm) A1FI 7.1 2, A1B 7.1 2, Scenario A1T A , , B B , The future depends on choices we re making now CO 2 is predicted to reach ppm by 2100 A1FI A1B A2 B1 Could be higher, if positive feedbacks are strong - Earth s climate has several tipping points Other GHGs will also increase 2

6 o C by 2100 History A1B A1FI A1T A2 B1 B2 3.0 o 4.6 o 2.

3 As a consequence, Earth s average temperature is predicted to rise by o C by 2100 History A1B A1FI A1T A2 B1 B2 3.0 o 4.6 o 2.6 o 4.0 o 2.0 o 2.7 o Earth will warm even if we stop emitting today A1B A2 A1FI B1 Zero emissions 0.6 o 3

Temperature rise is likely to persist for 1,000 years after we stop emitting greenhouse gasses Warming will be most severe in the arctic B1: Arctic warming of ~ 4 o

4 Temperature rise is likely to persist for 1,000 years after we stop emitting greenhouse gasses Warming will be most severe in the arctic B1: Arctic warming of ~ 4 o (global mean of 2 o ) A1B: Arctic warming of ~ 6 o (global mean of 3 o ) A2: Arctic warming of ~7-8 o (global mean of 4 o ) - Arctic is site of strongest positive feedbacks 4

Continued melting of the cryosphere - Arctic summer sea ice may disappear before 2100 What s happened over the last 21,000 years? www.youtube.com/watch?

5 Continued melting of the cryosphere - Arctic summer sea ice may disappear before 2100 What s happened over the last 21,000 years? The future projection is based on the assumption of complete cessation of carbon dioxide emissions in 2100 (~IPCC A2). Because future world population is uncertain, it was frozen at 7 billion people. 5

snowpacks for water supply - including 750,000,000 people in China and India

6 Many glaciers are likely to disappear by 2100, including all intertropical glaciers by more than a billion people rely on glaciers and seasonal snowpacks for water supply - including 750,000,000 people in China and India Continued loss of seasonal snowcover - largest decreases over western U.S. and eastern Europe 6

7 Continued loss of ice sheets - full melting of Greenland ice sheet 7 m sea level rise - full melting of Antarctic ice sheet 57 m sea level rise Permafrost will continue to thaw - top 25 m estimated to contain ~ Gt of carbon Gt currently in atmosphere 7

Tropical forests Temperate forests Boreal

8 Tundra permafrost contains more carbon than the aboveground vegetation of several major biomes Vegetation Soil Total Gigatons of Carbon Tropical forests Temperate forests Boreal forests Tropical savannas Temperate grasslands Deserts Tundra Wetlands Croplands - globally, >4 times more carbon in soils than in vegetation 8

9 Sea level rise of 1-2 meters by 2100 (?) - up to 300 million people could be flooded each year with 1 meter rise - at least 10 million/yr Southeast Asia and islands would be most affected 9

10 Much of U.S. would be affected by 1 meter rise Much of Florida would also be under water 10

11 So would much of the east coast Long-term sea level rise due to melting of ice sheets even if climate is stabilized 11

Continued later freezing and earlier break-up of lake and

period Altered precipitation patterns - small increase (5%)

variation Winter Summer - increases in high latitudes in

12 Continued later freezing and earlier break-up of lake and river ice - 3 week increase in summer lake stratification period Altered precipitation patterns - small increase (5%) in global precipitation - but much geographic and seasonal variation Winter Summer - increases in high latitudes in both seasons - but decreases in mid-latitude summer precipitation 12

13 Big increase in severe precipitation events - especially over NH land - flooding, erosion, disease Severe storms have increased in US since

14 Increased droughts also Land area in extreme drought predicted to increase from 1% 30% by 2100 in the A2 scenario in at least severe drought: 5% 40% in at least moderate drought: 20% 50% 14

15 Latitudinal gradient in winter precipitation in U.S. Summer rainfall is predicted to decrease throughout U.S. 15

16 US breadbasket could become largely unsuitable for agriculture Increased heat waves 16

17 The number of days >90 o will increase in Michigan The number of days >90 o will increase in Michigan 17

18 The number of days >90 o will increase in Michigan Large increases in extremely hot winters, summers, and years in US during Extremely Hot Winters Number hotter than a 1 in 20 year event during

Large increases in extremely hot winters, summers, and years in US during 2071-2100 Extremely Hot Winters Extremely Hot Summers Number hotter than a 1 in 20 year event during 1961-1990

19 Large increases in extremely hot winters, summers, and years in US during Extremely Hot Winters Extremely Hot Summers Number hotter than a 1 in 20 year event during Large increases in extremely hot winters, summers, and years in US during Extremely Extremely Hot Hot Years Summers Winters Number hotter than a 1 in 20 year event during

20 By 2100 in Europe, every other summer could be like 2003 >40,000 Europeans died from heat stress Future summers are very likely to be hotter than any experienced thus far 20

21 Future summers are very likely to be hotter than any experienced thus far Drought and famine especially in Africa 21

22 Fire frequency is predicted to increase in many areas Cessation of the Great Ocean Conveyor Belt? - if so, temporary cooling of North Atlantic Positive global feedback 22

23 Hmmm.. not likely Increased frequency of stronger hurricanes - 80% increase in Categories 4-5 over last 35 years, most likely due to warmer oceans 23

24 Most models predict increase in Category 5 hurricanes Storm surge would be much more damaging 24

25 What might Earth look like in the year 10,000? Bottom line: Current trends are expected to continue, but at an accelerating rate What is today an extreme event is likely to become commonplace If tipping points are reached, change may be more rapid, and less reversible, than predicted thus far 25

Chapter 2. Changes in Sea Level Melting Cryosphere Atmospheric Changes Summary IPCC (2013)

Chapter 2. Changes in Sea Level Melting Cryosphere Atmospheric Changes Summary IPCC (2013) IPCC (2013) Ice is melting faster (sea ice, glaciers, ice sheets, snow) Sea level is rising More ocean heat content More intense rainfall More severe drought Fewer frosts More heat waves Spring is arriving