Global Climate Change

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1 Global Climate Change 1 Climate Change Past Climate Trends Is the Earth Warming? Predictions of Climate Change Ocean Circulation and Sea Ice Vegetation Temperature Energy Policy and Greenhouse Gases 2 Is the Climate Really Changing? The Earth is currently at about the warmest it has been in the last ~1 million years, but is still ~10 C below what it was when the Dinosaurs were around million years ago. Global climate changes have not been more than 1 C/century, although the temperature in the Northern Hemisphere has changed by 5 7 C in a couple of decades. 3 Strong correlation between [CO2] and surface temperature over last 150 years 4

2 Strong correlation between [CO2] and surface temperature over last 1,000 years 5 Strong correlation between [CO2] and surface temperature over last 400,000 years Petit et al., Nature, 399, 429,

3 9 The recent temperature record shows warming that is becoming clearer and clearer. The cooler period from the mid 40s to the late 70s is thought to be due to an atmospheric oscillation the Pacific Decadal Oscillation The dip during is due to the eruption of Mt. Pinatubo. This is the overall relationship between the models and the temperature record: Another aspect of global warming: The Earth doesn t reach a new equilibrium immediately. Thermal inertia. It is estimated that the current temperature is 65 80% of the temperature that will be reached eventually if we stop increasing the radiative forcing. 12

4 There are several other lines of evidence that the Earth is warming. Rapid retreat of glaciers all over the world, Signatures of warming and/or freshening of water seen in the isotopic oxygen signatures in corals Increasing severe storms. There is lots of evidence that the Earth is warming, and these days most people are agreeing that there is observable warming. 13 June 3, 2002: Bush Administration s new Climate Report states that the United States will be substantially changed in the next few decades very likely seeing the disruption of snow-fed water supplies, more stifling heat waves and the permanent disappearance of Rocky Mountain meadows and coastal marshes, for example In the report, the administration for the first time mostly blames human actions for recent global warming. It says the main culprit is the burning of fossil fuels that send heat-trapping greenhouse gases into the atmosphere. New York Times 14 Bottom line: The heating of the planet is pretty much what we predict based on the effects of aerosols and greenhouse gases. 15 The Future... We can calculate rather precisely the additional forcing that more greenhouse gasses will add, and we are working really hard to figure out the effect of aerosols on the climate system. There is strong evidence that the Earth will continue to warm, and this will lead to effects that many people would consider unacceptable. 16

5 There are many aspects of the climate system that we really can t predict all that well, and these could lead to effects that are potentially even more catastrophic than the straightforward greenhouse warming/climate change Changes in Ocean Circulation Some models predict shutting down the formation of deep water in the North Atlantic. Deep water is only formed in a few places on the globe, and a major one is the North Atlantic. 18 Deep water forms as ocean currents bring salty water from the tropics (evaporation increases salinity) to the north. There the salty water is cooled, and the combination of high salinity and cold temperatures mean that this water can sink to the deep ocean. Exchange with the deep ocean takes a few thousand years. 19 Scenarios where the sea ice, which is fresh, melts, could stop deep water formation. Some models predict that the formation will return in ~100 years, some predict a permanent shut off. Either way, about 40% of the CO2 we emit is taken up by the ocean, and ultimately it is removed to the deep ocean. Shutting off the formation of deep water could cut off this large carbon sink. 20

6 Places where the water is cold enough and salty enough to form deep water: 21 Breakup of the West Antarctic Ice Sheet Floating ice that melts does not affect sea level. Why? A portion of the Antarctic ice sheet rests on the ocean floor. If it breaks up, and slides into the ocean, it will result in meters of sea level rise, rather than the feet that are predicted now. 22 The West Antarctic Ice Sheet (WAIS) keeps many glaciers from reaching the ocean. If the ice sheet breaks up, more glaciers (on land or on top of ice resting on the ocean floor) have easy access to the ocean creates more ice cubes. Islands that had been locked in by ice can now be circumnavigated for the first time. 23 Desertification It isn t completely clear how quickly ecosystems can migrate, but it is very likely it is not fast enough. If there is large-scale forest die-back, this will add large quantities of additional carbon into the atmosphere. 24

7 25 Change in annual temperatures for the 2050s Change in annual temperatures for the 2050s compared to present, when driven by an increase of 1%/yr of greenhouse gases climatic year vs average climatology

8 Annual runoff Percentage change in 30-year average annual runoff by the 2080s. University of Southampton

9 33 Crop yield change Percentage change in average crop yields for the climate change scenario. Effects of CO2 are taken into account. Crops modeled are: wheat, maize and rice. Changes shown are averaged for national or regional levels based on the economic components of the Basic Linked System. Jackson Institute, University College London / Goddard Institute for Space Studies / International Institute for Applied Systems Analysis 34 More on Greenhouse Gases 35 36

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11 Total EJ: 186,000. Global energy consumption: 424 EJ in Energy use and its ratio to GDP in the US from 1949 to Energy demand remained flat from 1973 to 1986, but has begun to rise in recent years. The decrease in energy per dollar of GDP (in 1996 dollars) shows that our economy continues to become more efficient. 42 Estimates of carbon savings and costs predicted to be achievable by different sectors of the US economy. Negative costs indicate that the introduction of energy-efficient, low-carbon technologies costs less than the energy they save

12 45 46 Regional Greenhouse Gas Initiative (RGGI) The Regional Greenhouse Gas Initiative (RGGI) is a cooperative effort by Northeast and Mid-Atlantic states (currently CT, DE, ME, NH, NJ, NY, & VT) to discuss the design of a regional cap-and-trade program initially covering carbon dioxide emissions from power plants in the region. 47 In the future, RGGI may be extended to include other sources of greenhouse gas emissions, and greenhouse gases other than CO2. Goals: Stabilize emissions by 2015 Achieve 10% reduction in emissions by 2019 Allows power plants to reduce emissions or buy credits on the market 48

13 Western Regional Climate Action Initiative Requires Arizona, California, New Mexico, Oregon, and Washington to develop a regional target in 6 months to reduce greenhouse emissions. Agreement signed Feb Similar to RGGI Devise market-based plan to reach target goals Track and manage regional greenhouse gas emissions California: 25% reduction in emissions by