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This article recommends the key design elements of US climate law. Much past environmental law has suffered from four design problems: fragmentation, insensitivity to tradeoffs, rigid prescriptive commands, and mismatched scale. These are problems with the design of regulatory systems, not a rejection of the overall objective of environmental law to protect ecosystems and human health. These four design defects raised the costs, reduced the benefits, and increased the countervailing risks of many past environmental laws. The principal environmental laws successfully enacted since the 1990s, such as the acid rain trading program in the 1990 Clean Air Act (CAA) Amendments and the 1996 Safe Drinking Water Act amendments, were consciously designed to overcome the prior design defects. New law for climate change should improve on the design of past environmental law, fostering four counterpart solutions to the prior design defects: cross-cutting integration instead of fragmentation, attention to tradeoffs instead of their neglect, flexible incentive-based policy instruments such as emissions trading in place of rigid prescriptive commands, and optimal instead of mismatched scale. This article advocates a design for U.S. climate policy that embodies these four design solutions. It proposes a policy that is comprehensive in its coverage of multiple pollutants (all GHGs), their sources and sinks; multiple sectors (indeed economy-wide); and multiple issues currently divided among separate agencies. It advocates explicit attention to tradeoffs, both benefit-cost and risk-risk (including both ancillary harms and ancillary benefits), in setting the goals and boundaries of climate policy. It advocates the use of flexible market-based incentives through an efficient cap-and-trade system, with most allowances auctioned along multi-year emissions reduction schedules that are reviewed periodically in light of new information. And it advocates matching the legal regime to the environmental and economic scale of the climate problem, starting at the global level, engaging all the major emitting countries (including the U.S. and China), and then implementing at the national and sub-national levels rather than a patchwork bottom-up approach. In so doing it addresses the roles of EPA regulation under the current CAA and of new legislation. It argues that among environmental issues, climate change is ideally suited to adopt these improved policy design features.

In this work, the effect of the aerosol vertical distribution on the local shortwave aerosol radiative forcing is studied. We computed the radiative forcing at the top and bottom of the atmosphere between 0.2 and 4 microns using the libRadTran package and compared the results with those provided by AERONET (AErosol RObotic NETwork). Lidar measurements were employed to characterize the aerosol vertical profile, and collocated AERONET measurements provided aerosol optical parameters required to calculate its radiative forcing. A good correlation between the calculated radiative forcings and those provide by AERONET, with differences smaller than 1 W m-2 (15% of estimated radiative forcing), is obtained when a gaussian vertical aerosol profile is assumed. Notwithstanding, when a measured aerosol profile is inserted into the model, differences between radiative forcings can vary up to 6.54Wm-2 (15%), with a mean of differences =-0.74±3.06W m-2 at BOA and -3.69Wm-2 (13%), with a mean of differences = -0.27±1.32Wm-2 at TOA due to multiple aerosol layers and aerosol types. These results indicate that accurate information about aerosol vertical distribution must be incorporated in the radiative forcing calculation in order to reduce its uncertainties. ; This research was funded by European Union's Horizon 2020 research and innovation programme through project ACTRIS-2 (grant 654109), the Spanish Ministry of Economy and Competitivity (CRISOL, CGL2017-85344-R and ACTRIS-ESPAÑA, CGL2017-90884-REDT) and Madrid Regional Government (TIGAS-CM, Y2018/EMT-5177).

International audience ; Knowing the historical relative contribution of greenhouse gases (GHGs) and short-lived climate forcers (SLCFs) to global radiative forcing (RF) at the regional level can help understand how future GHGs emission reductions and associated or independent reductions in SLCFs will affect the ultimate purpose of the Paris Agreement. In this study, we use a compact Earth system model to quantify the global RF and attribute global RF to individual countries and regions. As our evaluation, the United States, the first 15 European Union members, and China are the top three contributors, accounting for 21.9 ± 3.1%, 13.7 ± 1.6%, and 8.6 ± 7.0% of global RF in 2014, respectively. We also find a contrast between developed countries where GHGs dominate the RF and developing countries where SLCFs including aerosols and ozone are more dominant. In developing countries, negative RF caused by aerosols largely masks the positive RF from GHGs. As developing countries take measures to improve the air quality, their negative contributions from aerosols will likely be reduced in the future, which will in turn enhance global warming. This underlines the importance of reducing GHG emissions in parallel to avoid any detrimental consequences from air quality policies.

International audience ; Knowing the historical relative contribution of greenhouse gases (GHGs) and short-lived climate forcers (SLCFs) to global radiative forcing (RF) at the regional level can help understand how future GHGs emission reductions and associated or independent reductions in SLCFs will affect the ultimate purpose of the Paris Agreement. In this study, we use a compact Earth system model to quantify the global RF and attribute global RF to individual countries and regions. As our evaluation, the United States, the first 15 European Union members, and China are the top three contributors, accounting for 21.9 ± 3.1%, 13.7 ± 1.6%, and 8.6 ± 7.0% of global RF in 2014, respectively. We also find a contrast between developed countries where GHGs dominate the RF and developing countries where SLCFs including aerosols and ozone are more dominant. In developing countries, negative RF caused by aerosols largely masks the positive RF from GHGs. As developing countries take measures to improve the air quality, their negative contributions from aerosols will likely be reduced in the future, which will in turn enhance global warming. This underlines the importance of reducing GHG emissions in parallel to avoid any detrimental consequences from air quality policies.

International audience ; Knowing the historical relative contribution of greenhouse gases (GHGs) and short-lived climate forcers (SLCFs) to global radiative forcing (RF) at the regional level can help understand how future GHGs emission reductions and associated or independent reductions in SLCFs will affect the ultimate purpose of the Paris Agreement. In this study, we use a compact Earth system model to quantify the global RF and attribute global RF to individual countries and regions. As our evaluation, the United States, the first 15 European Union members, and China are the top three contributors, accounting for 21.9 ± 3.1%, 13.7 ± 1.6%, and 8.6 ± 7.0% of global RF in 2014, respectively. We also find a contrast between developed countries where GHGs dominate the RF and developing countries where SLCFs including aerosols and ozone are more dominant. In developing countries, negative RF caused by aerosols largely masks the positive RF from GHGs. As developing countries take measures to improve the air quality, their negative contributions from aerosols will likely be reduced in the future, which will in turn enhance global warming. This underlines the importance of reducing GHG emissions in parallel to avoid any detrimental consequences from air quality policies.

International audience ; Knowing the historical relative contribution of greenhouse gases (GHGs) and short-lived climate forcers (SLCFs) to global radiative forcing (RF) at the regional level can help understand how future GHGs emission reductions and associated or independent reductions in SLCFs will affect the ultimate purpose of the Paris Agreement. In this study, we use a compact Earth system model to quantify the global RF and attribute global RF to individual countries and regions. As our evaluation, the United States, the first 15 European Union members, and China are the top three contributors, accounting for 21.9 ± 3.1%, 13.7 ± 1.6%, and 8.6 ± 7.0% of global RF in 2014, respectively. We also find a contrast between developed countries where GHGs dominate the RF and developing countries where SLCFs including aerosols and ozone are more dominant. In developing countries, negative RF caused by aerosols largely masks the positive RF from GHGs. As developing countries take measures to improve the air quality, their negative contributions from aerosols will likely be reduced in the future, which will in turn enhance global warming. This underlines the importance of reducing GHG emissions in parallel to avoid any detrimental consequences from air quality policies.

Possible connections are studied between the monthly average values of the wind angular moment module and anomalу of the globally averaged surface temperature and change in radiative forcing. The existence of statistically significant positive linear correlation between these characteristics is shown. The results obtained are in accordance with the conclusions of the theory of similarity of planetary atmospheres.

We apply different aerosol and aerosol precursor emission scenarios reflecting possible future control strategies for air pollution in the ECHAM5-HAM model, and simulate the resulting effect on the Earth's radiation budget. We use two opposing future mitigation strategies for the year 2030: one in which emission reduction legislation decided in countries throughout the world are effectively implemented (current legislation; CLE 2030) and one in which all technical options for emissions reductions are being implemented independent of their cost (maximum feasible reduction; MFR 2030). We consider the direct, semi-direct and indirect radiative effects of aerosols. The total anthropogenic aerosol radiative forcing defined as the difference in the top-of-the-atmosphere radiation between 2000 and pre-industrial times amounts to -2.00 W/m². In the future this negative global annual mean aerosol radiative forcing will only slightly change (+0.02 W/m²) under the "current legislation" scenario. Regionally, the effects are much larger: e.g. over Eastern Europe radiative forcing would increase by +1.50 W/m² because of successful aerosol reduction policies, whereas over South Asia it would decrease by -1.10 W/m² because of further growth of emissions. A "maximum feasible reduction" of aerosols and their precursors would lead to an increase of the global annual mean aerosol radiative forcing by +1.13 W/m². Hence, in the latter case, the present day negative anthropogenic aerosol forcing could be more than halved by 2030 because of aerosol reduction policies and climate change thereafter will be to a larger extent be controlled by greenhouse gas emissions. We combined these two opposing future mitigation strategies for a number of experiments focusing on different sectors and regions. In addition, we performed sensitivity studies to estimate the importance of the aerosol microphysical coupling within the range of expected future changes. For changes in oxidant concentrations caused by future air pollution mitigationm we do not ...

International audience ; We apply different aerosol and aerosol precursor emission scenarios reflecting possible future control strategies for air pollution in the ECHAM5-HAM model, and simulate the resulting effect on the Earth's radiation budget. We use two opposing future mitigation strategies for the year 2030: one in which emission reduction legislation decided in countries throughout the world are effectively implemented (current legislation; CLE 2030) and one in which all technical options for emission reductions are being implemented independent of their cost (maximum feasible reduction; MFR 2030). We consider the direct, semi-direct and indirect radiative effects of aerosols. The total anthropogenic aerosol radiative forcing defined as the difference in the top-of-the-atmosphere radiation between 2000 and pre-industrial times amounts to ?2.05 W/m 2 . In the future this negative global annual mean aerosol radiative forcing will only slightly change (+0.02 W/m 2 ) under the "current legislation" scenario. Regionally, the effects are much larger: e.g. over Eastern Europe radiative forcing would increase by +1.50 W/m 2 because of successful aerosol reduction policies, whereas over South Asia it would decrease by ?1.10 W/m 2 because of further growth of emissions. A "maximum feasible reduction" of aerosols and their precursors would lead to an increase of the global annual mean aerosol radiative forcing by +1.13 W/m 2 . Hence, in the latter case, the present day negative anthropogenic aerosol forcing cloud be more than halved by 2030 because of aerosol reduction policies and climate change thereafter will be to a larger extend be controlled by greenhouse gas emissions. We combined these two opposing future mitigation strategies for a number of experiments focusing on different sectors and regions. In addition, we performed sensitivity studies to estimate the importance of future changes in oxidant concentrations and the importance of the aerosol microphysical coupling within the range of expected future ...