TODAY’S STUDY: WITH EMISSIONS RISING, THE SITUATION IS STARK
2014 Energy and Climate Outlook
November 2014 (The Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change)
[editor’s note: Important content, awful graphics. Sorry.]
Changes in Energy and Emissions
With emissions stable and falling in developed countries, on the assumption that Copenhagen-Cancun pledges are met and retained in the post‑2020 period, future emissions growth will come from the Other G20 and developing countries.
• Growth in global emissions results in 77 Gt (gigatons) carbon dioxide equivalent (CO2‑eq)1 emissions in 2050, rising to 92 Gt by 2100—nearly double the emissions in 2010. By 2050 the developed countries account for about 15% of global emissions, down from 30% in 2010.
• CO2 emissions from fossil fuels remain the largest source of GHGs, but other greenhouse gas emissions and non‑fossil energy sources of CO2 account for almost 33% of total global GHG emissions by 2100 (slightly down from 35% in 2010, and 43% in 2050).
• In 2050, electricity and transportation emissions will together account for nearly 52% of global CO2 emissions from fossil fuel use, decreasing slightly from 56% in 2010.
• Fossil fuel energy continues to account for over 80% of primary energy through 2050 (despite rapid growth in renewables and nuclear), in part because the natural gas share of primary energy also increases. Changes in Climate Global change will accelerate with changes in global and regional temperatures, precipitation, land use, sea level rise and ocean acidification.
• Global mean sur face temperature increase ranges from 1.6 to 2.6°C (central estimate 1.9°C) by mid‑century relative to the 1901–1950 mean, and 3.3 to 5.6°C (central estimate 3.9°C) by 2100.
• Global mean precipitation increase ranges from 4.1 to 5.3% by 2050 relative to the 1901–1950 mean, and 7.5 to 12.4% (central estimate 8.5%) by 2100.
• Thermal expansion and land glacier melting contribute 0.08 to 0.12 meters to sea level rise from present (2014) by 2050, and 0.25 to 0.44 meters (central estimate 0.30 meters) by 2100.
• More carbon in the ocean leads to increasing acidity—average pH drops from 8.03 in 2010 to about 7.85 pH by 2100. Changes in Water Flows Annual freshwater flow increases globally by about 15% by 2100.
• By the end of the century, total water withdrawals are projected to increase by about 19%. We estimate current withdrawals of 2,700 billion cubic meters (bcm) rising to 3,200 bcm in 2100. At this level, withdrawals would account for about 6% of the annual freshwater flow.
• Our projections assume no changes in irrigated lands and, as a result, withdrawal for irrigation falls slightly (from the current 1,551 bcm to 1,389 bcm in 2100). Withdrawals for domestic use of water doubles (from 348 to 698 bcm) and industrial use of water increases by almost 45% (from 763 to 1,098 bcm).
• We distinguish between consumption of water (the amount lost to evaporation or consumed and not returned to the basin) and withdrawals, which include consumption plus return flow. In terms of consumption, annual irrigation is projected to use nearly 1,000 bcm in 2100, while industrial and domestic uses are each about 1/5 of that amount— just over 200 bcm. Globally, this level of consumption is 2.5% of total annual freshwater flow in 2100.
• Withdrawals and consumption as a percentage of total annual flows can provide a misleading picture of the adequacy of water resources, because location and timing of flows is important. Similarly, the seasonality of precipitation often means the timing of flows does not match needs.
• By 2100, our scenarios show reductions in potential water stress in some parts of North America, China and the Middle East. Despite abundant global supply, they also show increased water stress in parts of India, China, Pakistan, Turkey, North Africa, South Africa and the U.S.
• Based on more extensive simulations, water requirements increasing with population and GDP can have a stronger effect than climatic changes on water stress, especially in developing countries, where economic and population growth can be strong drivers of water requirements. Where growth occurs, inter-basin transfers, added water storage, and conservation and efficiency measures can be a response to increased stress.
• Projections of regional precipitation patterns, and the processes that control runoff and water requirements, are highly uncertain and have strong interannual and decadal variability. More rigorous uncertainty analysis is needed to fully understand likelihoods of specific water resource outcomes. Expectations for the 2015 UN Climate Agreement
• Likely efforts will further bend the curve of emissions growth, with an estimate of 68 Gt CO2‑eq emissions in 2050—about 9 Gt less than our Outlook estimate for 2050.
• Unless the post‑2020 agreement is significantly more stringent than we speculate, the emissions path will diverge further from what the Intergovernmental Panel on Climate Change (IPCC) Working Group III shows to be consistent with stabilization of GHG concentrations to 530–580 CO2‑eq by 2100.
• On this emissions path, by 2030 the world will be within about 7 years of hitting cumulative emissions levels that the IPCC Working Group I shows to be consistent with a 50% chance of holding temperature increase to less than 2°C. Progress on climate change mitigation through international agreement has been slow, and efforts appear to be falling well behind the ambitious long‑term goals set by the international community.
Whether those goals are achieved or not, any hope of averting considerable climate consequences by stabilizing atmospheric GHG concentrations will require significant emissions reduction. Another 20 or 30 years of increasing emissions suggest substantial risks of dangerous climate change.
This Outlook provides an overview of the details by which we have reached these broad conclusions. A principal product of our process is a set of detailed tables containing economic, energy, land use, and emissions results for each of 16 global regions.2
We provide detailed regional projections up to 2050 and show global results through 2100 (useful for providing long‑term climate implications of our near‑term emissions policy choices). The nature of the climate change issue—(1) the long‑term accumulation of gases with long lifetimes; (2) a climate system with inertia so that it takes some decades to millennia, in the case of sea level, to see the full effect of current concentrations; and (3) the added inertia in the energy system due to long‑lived capital investments and the institutions that can be slow to change— all mean that much of our climate future for the next few decades has already been determined; we are just waiting to see how uncertainties about the climate response resolve themselves…