http://hdl.handle.net/1721.1/3550 Report Series intended to communicate research results, and provide useful reviews and commentaries on various aspects of the global climate change issue. Tue, 18 Jun 2013 21:37:20 GMT 2013-06-18T21:37:20Z http://dspace.mit.edu:80/bitstream/id/790611/ http://hdl.handle.net/1721.1/3550 http://hdl.handle.net/1721.1/79081 Climate Change Impacts on Extreme Events in the United States: An Uncertainty Analysis Monier, Erwan; Gao, Xiang Extreme weather and climate events, such as heat waves, droughts and severe precipitation events, have substantial impacts on ecosystems and the economy. However, future climate simulations display large uncertainty in mean changes. As a result, the uncertainty in future changes of extreme events, especially at the local and national level, is large. In this study, we analyze changes in extreme events over the US in a 60-member ensemble simulation of the 21st century with the Massachusetts Institute of Technology (MIT) Integrated Global System Model–Community Atmosphere Model (IGSM-CAM). Four values of climate sensitivity, three emissions scenarios and five initial conditions are considered. The results show a general intensification of extreme daily maximum temperatures and extreme precipitation events over most of the US. The number of rain days per year increases over the Great Plains but decreases in the northern Pacific Coast and along the Gulf Coast. Extreme daily minimum temperatures increase, especially over the northern parts of the US. As a result, the number of frost days per year decreases over the entire US and the frost-free zone expands northward. This study displays a wide range of future changes in extreme events in the US, even simulated by a single climate model. Nonetheless, it clearly shows that under a reference emissions scenario with no climate policy, changes in extreme events reach dangerous levels, especially for large values of climate sensitivity. On the other hand, the implementation of a stabilization scenario drastically reduces the changes in extremes, even for the highest climate sensitivity considered. Wed, 01 May 2013 00:00:00 GMT http://hdl.handle.net/1721.1/79081 2013-05-01T00:00:00Z http://hdl.handle.net/1721.1/79080 A Framework for Modeling Uncertainty in Regional Climate Change Monier, Erwan; Gao, Xiang; Scott, Jeffery; Sokolov, Andrei; Schlosser, C. Adam In this study, we present a new modeling framework and a large ensemble of climate projections to investigate the uncertainty in regional climate change over the US associated with four dimensions of uncertainty. The sources of uncertainty considered in this framework are the emissions projections (using different climate policies), climate system parameters (represented by different values of climate sensitivity and net aerosol forcing), natural variability (by perturbing initial conditions) and structural uncertainty (using different climate models). The modeling framework revolves around the Massachusetts Institute of Technology (MIT) Integrated Global System Model (IGSM), an integrated assessment model with an intermediate complexity earth system model (with a two-dimensional zonal-mean atmosphere). Regional climate change over the US is obtained through a two-pronged approach. First, we use the IGSM-CAM framework which links the IGSM to the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). Secondly, we use a pattern-scaling method that extends the IGSM zonal mean based on climate change patterns from various climate models. Results show that uncertainty in temperature changes are mainly driven by policy choices and the range of climate sensitivity considered. Meanwhile, the four sources of uncertainty contribute more equally to precipitation changes, with natural variability having a large impact in the first part of the 21st century. Overall, the choice of policy is the largest driver of uncertainty in future projections of climate change over the US. Wed, 01 May 2013 00:00:00 GMT http://hdl.handle.net/1721.1/79080 2013-05-01T00:00:00Z http://hdl.handle.net/1721.1/79079 Integrated Economic and Climate Projections for Impact Assessment Paltsev, Sergey; Monier, Erwan; Scott, Jeffery; Sokolov, Andrei; Reilly, John M. We designed scenarios for impact assessment that explicitly address policy choices and uncertainty in climate response. Economic projections and the resulting greenhouse gas emissions for the “no climate policy” scenario and two stabilization scenarios: at 4.5 W/m2 and 3.7 W/m2 by 2100 are provided. They can be used for a broader climate impact assessment for the US and other regions, with the goal of making it possible to provide a more consistent picture of climate impacts, and how those impacts depend on uncertainty in climate system response and policy choices. The long-term risks, beyond 2050, of climate change can be strongly influenced by policy choices. In the nearer term, the climate we will observe is hard to influence with policy, and what we actually see will be strongly influenced by natural variability and the earth system response to existing greenhouse gases. In the end, the nature of the system is that a strong effect of policy, especially directed toward long-lived GHGs, will lag by 30 to 40 years its implementation. Wed, 01 May 2013 00:00:00 GMT http://hdl.handle.net/1721.1/79079 2013-05-01T00:00:00Z http://hdl.handle.net/1721.1/78302 The Energy and CO2 Emissions Impact of Renewable Energy Development in China Zhang, X.; Qi, T.; Karplus, V.J. China’s recently-adopted targets for developing renewable electricity—wind, solar, and biomass—would require expansion on an unprecedented scale in China and relative to existing global installations. An important question is how far this deployment will go toward achieving China’s low carbon development goals, which include a carbon intensity reduction target of 40–45% relative to 2005 and a non-fossil primary energy target of 15% by 2020. During the period from 2010 to 2020, we find that current renewable electricity targets result in significant additional renewable energy installation and a reduction in cumulative CO2 emissions of 1.2% relative to a no policy baseline. After 2020, the role of renewables is sensitive to both economic growth and technology cost assumptions. Importantly, we find that CO2 emissions reductions due to increased renewables are offset in each year by emissions increases in non-covered sectors through 2050. By increasing reliance on renewable energy sources in the electricity sector, fossil fuel demand in the power sector falls, resulting in lower fossil fuel prices, which in turn leads to greater demand for these fuels in unconstrained sectors. We consider sensitivity to renewable electricity cost after 2020 and find that if cost falls due to policy or other reasons, renewable electricity share increases and results in slightly higher economic growth through 2050. However, regardless of the cost assumption, projected CO2 emissions reductions are very modest under a policy that only targets the supply side in the electricity sector. A policy approach that covers all sectors and allows flexibility to reduce CO2 at lowest cost—such as an emissions trading system—will prevent this emissions leakage and ensure targeted reductions in CO2 emissions are achieved over the long term. Mon, 01 Apr 2013 00:00:00 GMT http://hdl.handle.net/1721.1/78302 2013-04-01T00:00:00Z