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The Paris pledges are unique documents in climate governance that outline what each country intends to do to combat climate change. Often, these documents contain headline greenhouse gas percentage reduction targets that appear to summarize countries' contributions to mitigation. This is a boon for comparative climate policy research. However, I show in this paper that the Paris pledges require detailed interpretation to be comparable. I demonstrate the risks in comparing these targets by re-visiting a recent studying linking national public opinion to the stringency of countries' mitigation goals. I develop new indicators that better account for the structure of the targets and show in replications that the original finding is inconsistent with the underlying data. I conclude by drawing lessons for studying the Paris pledges. [ABSTRACT FROM AUTHOR]

Over the last few years, California has passed some of the strongest climate policies in the USA. These new policies have been motivated in part by increasing concerns over the risk of climate-related impacts and facilitated by the state's existing framework of energy and air quality policies. This paper presents an overview of the evolution of this increased awareness of climate change issues by policy makers brought about by the strong link between climate science and policy in the state. The State Legislature initiated this link in 1988 with the mandate to prepare an assessment of the potential consequences of climate change to California. Further interactions between science and policy has more recently resulted, in summer of 2006, in the passage of Assembly Bill 32, a law that limits future greenhouse gas emissions in California. This paper discusses the important role played by a series of state and regional climate assessments beginning in 1988 and, in particular, the lessons learned from a recently completed study known as the Scenarios Project. [ABSTRACT FROM AUTHOR]

wide variety of scenarios for future development have played significant roles in climate policy discussions. This paper presents projections of greenhouse gas (GHG) concentrations, sea level rise due to thermal expansion and glacial melt, oceanic acidity, and global mean temperature increases computed with the MIT Integrated Global Systems Model (IGSM) using scenarios for twenty-first century emissions developed by three different groups: intergovernmental (represented by the Intergovernmental Panel on Climate Change), government (represented by the U.S. government Climate Change Science Program) and industry (represented by Royal Dutch Shell plc). In all these scenarios the climate system undergoes substantial changes. By 2100, the CO concentration ranges from 470 to 1020 ppm compared to a 2000 level of 365 ppm, the CO-equivalent concentration of all greenhouse gases ranges from 550 to 1780 ppm in comparison to a 2000 level of 415 ppm, oceanic acidity changes from a current pH of around 8 to a range from 7.63 to 7.91, in comparison to a pH change from a preindustrial level by 0.1 unit. The global mean temperature increases by 1.8 to 7.0°C relative to 2000. Such increases will require considerable adaptation of many human systems and will leave some aspects of the earth's environment irreversibly changed. Thus, the remarkable aspect of these different approaches to scenario development is not the differences in detail and philosophy but rather the similar picture they paint of a world at risk from climate change even if there is substantial effort to reduce emissions. [ABSTRACT FROM AUTHOR]

This paper investigates the uncertainty in the impact of climate change on flood frequency in England, through the use of continuous simulation of river flows. Six different sources of uncertainty are discussed: future greenhouse gas emissions; Global Climate Model (GCM) structure; downscaling from GCMs (including Regional Climate Model structure); hydrological model structure; hydrological model parameters and the internal variability of the climate system (sampled by applying different GCM initial conditions). These sources of uncertainty are demonstrated (separately) for two example catchments in England, by propagation through to flood frequency impact. The results suggest that uncertainty from GCM structure is by far the largest source of uncertainty. However, this is due to the extremely large increases in winter rainfall predicted by one of the five GCMs used. Other sources of uncertainty become more significant if the results from this GCM are omitted, although uncertainty from sources relating to modelling of the future climate is generally still larger than that relating to emissions or hydrological modelling. It is also shown that understanding current and future natural variability is critical in assessing the importance of climate change impacts on hydrology. [ABSTRACT FROM AUTHOR]

In addition to reducing greenhouse gas emissions, actions to achieve a sustainable coexistence with wildfire need to be taken now. In this paper we suggest several important policy, planning, and management changes that should be made, regardless of the many uncertainties in predicting future fire regimes. Similar to how other natural hazards are addressed, a risk-based framework for fire-related decisions is crucial. Reintroduction of fire to fire-prone ecosystems, careful use of fire surrogates, and creation of new and flexible policies will be needed for successful ecosystem management. Growing incompatibilities between urban development and wildfire also require a serious reevaluation of urban planning and building in fire-prone locations to reach a sustainable coexistence with fire. Our future cities and communities must be less susceptible to wildfire damage, and the ecosystems upon which we depend must be made more resilient to further disruptions in fire regimes. [ABSTRACT FROM AUTHOR]

The greenhouse gas emissions scenarios published by the IPCC in the Special Report on Emission Scenarios (SRES) continue to serve as a primary basis for assessing future climate change and possible response strategies. These scenarios were developed between 1996 and 1999 and sufficient time has now passed to make it worth examining their consistency with more recent data and projections. The comparison performed in this paper includes population, GDP, energy use, and emissions of CO2, non-CO2 gases and sulfur. We find the SRES scenarios to be largely consistent with historical data for the 1990-2000 period and with recent projections. Exceptions to this general observation include (1) in the long-term, relatively high population growth assumptions in some regions, particularly in the A2 scenario; (2) in the medium-term, relatively high economic growth assumptions in the LAM (Latin America, Africa and Middle East) region in the A1 scenario; (3) in the short-term, CO2 emissions projections in Al that are somewhat higher than the range of current scenarios; and (4) substantially higher sulfur emissions in some scenarios than in historical data and recent projections. In conclusion, given the relatively small inconsistencies for use as global scenarios there seems to be no immediate need for a large-scale IPCC-led update of the SRES scenarios that is solely based on the SRES scenario performance vis-a-vis data for the 1990-2000 period and/or more recent projections. Based on reported findings, individual research teams could make, and in some cases already have made, useful updates of the scenarios. [ABSTRACT FROM AUTHOR]