Global Climate Change 4

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1 Global Climate Change 4 Climate Change Consequences Climate Change Mitigation Climate Change Politics Tipping points

2 GAT: we re heating up

3 Hockey stick graph past 1000 years 2001 Data from thermometers (red) and from tree rings, corals, ice cores, and historical records (blue). The latter are referred to as proxy data.

4 IPCC Reports First Assessment Report in 1990 Second Assessment Report (SAR) in 1995 Third Assessment Report (TAR) in 2001 Fourth Assessment Report (AR4) in 2007

5 2001

6 2007

7 2007 AR4 Summary for Policymakers Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level. Global GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.

8 More Global atmospheric concentrations of CO2, methane (CH4) and nitrous oxide (N2O) have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations. It is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent (except Antarctica). Advances since the TAR show that discernible human influences extend beyond average temperature to other aspects of climate.

9 IPCC assessment 2001 The global average surface temperature has increased since Over the 20th century the increase has been 0.6±0.2 C. Globally, it is very likely (90-99% chance) that the 1990s was the warmest decade and 1998 the warmest year in the instrumental record, since New analyses of proxy data for the Northern Hemisphere indicate that the increase in the 20th century is likely (66-90%) to have been the largest of any century during the past 1,000 years. There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.

10 2007

11 2001

12 2001

13 2001

14 2007 LOSU level of scientific understanding

15 2007

16 IPCC Scenarios A1: rapid and successful economic development, in which current distinctions between "poor" and "rich" countries eventually dissolve A2: economic growth is uneven and the income gap between nowindustrialized and developing parts of the world does not narrow B1: high level of environmental and social consciousness combined with a globally coherent approach to a more sustainable development B2: government policies and business strategies at the national and local levels are influenced by environmentally aware citizens, with a trend toward local self-reliance and stronger communities

17 2007

18 Consequences of Global Warming Coastal changes Storms and Floods Changes to ENSO (El Nino-Southern Oscillation) Human Health Impact Biodiversity losses Agricultural changes

19 2007

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21 2001

22 2007

23 Possible ENSO Changes 2001

24 Pictures now and then

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26 Mitigation of Global Warming Energy conservation (efficiency) Nuclear energy Renewable energy CO 2 removal/sequestration in industrial processes Seeding the ocean with iron Cool the earth by screening sunlight Re-forestation Iron hypothesis: fertilizing world s oceans with iron to stimulate ocean photosynthesis

27 Political Issues & Global Warming Kyoto protocol (December 1997) Cut emissions to 94.8% of 1990 levels by Bonn 2001: 186 countries ratify Kyoto protocol some cuts reduced from 5.2% to only 1-3% US produces ~25% of CO 2, has signed but not ratified India is exempted

28 Kyoto Treaty Status

29 James Hansen (NASA) Mt. Pinatubo Scientific American, March 2004, p.68. Notes that ice core data show that the change in climate forcing between the ice age and today is about 6.5 W/ m 2. This forcing maintains a global temperature change of 5 degrees C, implying a climate sensitivity of 0.75±0.25 degrees C per W/m 2 Climate models have similar sensitivity Net value of added forcings since 1850 is 1.6±1.0 W/m 2. Evidence 1.6 W/m 2 is approximately correct from agreement between observed climate and calculations. Even more important: heat gain oceans last 50 yrs is consistent with the estimated NET forcing of 0.5 W/m 2 (so most of the imbalance goes to heating the oceans). Suggests: We re sitting on a time bomb Response of ice sheets Last ice agemore than 14,000 km 3 a yr melting of ice 1 meter of sea level per 20 yr for several centuries 1 meter sea level 1 W/m 2 radiative forcing for 12 yrs Time bomb Rise in sea level may lift ice sheets spectacular melting (not in IPCC reports) Warns: Highest level of additional warming should not be more than 1 C ~ 1 W/m 2

30 Abrupt changes are possible A small forcing can cause a small [climate] change or a huge one. National Academy of Sciences, Richard Alley, Scientific American, November 2004, p.62 Climate has suddenly flip-flopped in the past and will surely do so again From ice core data: huge temperature swings in very short times Other example: Regional droughts for decades (evidence from the past) Change in ocean circulation

31 Sudden temperature change in Greenland

32 Ice core data 2001

33 What now? Kyoto can only be the beginning Much larger reductions are probably necessary Challenge? Yes, but there are also opportunities... (Friedman)