Two themes dominating today's climate discussions are that "the science is settled," and "the science drives the policy." In reality, neither is generally true: The claim that the science of climate change is “settled” beyond dispute is belied by the almost-weekly publication of peer-reviewed research that is inconsistent with or directly contradicts the conventional narrative of catastrophic climate change. Likewise, economists and policy analysts are sharply divided about the best framework for understanding public policy responses, often because they interpret scientific inputs differently.

The purpose of this site is to gather notable scientific articles and commentary that we think are under-reported in the media, and to bring attention to important articles on economic and policy analysis of the issue. This site will be updated on a rolling basis, with the most recently published research appearing first.

Science Articles A Mathematical Analysis of the Divergence Problem in Dendroclimatology Craig Loehle Climatic Change Accepted for publication; June 2008 Abstract Tree rings provide a primary data source for reconstructing past climates, particularly over the past 1,000 years. However, divergence has been observed in twentieth century reconstructions. Divergence occurs when trees show a positive response to warming in the calibration period but a lesser or even negative response in recent decades. The mathematical implications of divergence for reconstructing climate are explored in this study. Divergence results either because of some unique environmental factor in recent decades, because trees reach an asymptotic maximum growth rate at some temperature, or because higher temperatures reduce tree growth. If trees show a nonlinear growth response, the result is to potentially truncate any historical temperatures higher than those in the calibration period, as well as to reduce the mean and range of reconstructed values compared to actual. This produces the divergence effect. This creates a cold bias in the reconstructed record and makes it impossible to make any statements about how warm recent decades are compared to historical periods. Some suggestions are made to overcome these problems. Ancient Permafrost and A Future, Warmer Arctic Duane G. Froese, et al. Science, 321:5896 September 2008 Abstract Climate models predict extensive and severe degradation of permafrost in response to global warming, with a potential for release of large volumes of stored carbon. However, the accuracy of these models is difficult to evaluate because little is known of the history of permafrost and its response to past warm intervals of climate. We report the presence of relict ground ice in subarctic Canada that is greater than 700,000 years old, with the implication that ground ice in this area has survived past interglaciations that were warmer and of longer duration than the present interglaciation. Climatic and Anthropogenic Factors Affecting River Discharge to the Global Ocean, 1951–2000 J.D. Milliman, et al. Global and Planetary Change June 2008 Abstract During the last half of the 20th century, cumulative annual discharge from 137 representative rivers (watershed areas ranging from 0.3 to 6300 × 103 km2) to the global ocean remained constant, although annual discharge from about one-third of these rivers changed by more than 30%. Discharge trends for many rivers reflected mostly changes in precipitation, primarily in response to short- and longer-term atmospheric–oceanic signals; with the notable exception of the Parana, Mississippi, Niger and Cunene rivers, few of these “normal" rivers experienced significant changes in either discharge or precipitation. Cumulative discharge from many mid-latitude rivers, in contrast, decreased by 60%, reflecting in large part impacts due to damming, irrigation and interbasin water transfers. A number of high-latitude and high-altitude rivers experienced increased discharge despite generally declining precipitation. Poorly constrained meteorological and hydrological data do not seem to explain fully these “excess” rivers; changed seasonality in discharge, decreased storage and/or decreased evapotranspiration also may play important roles. Simulated Reduction in Atlantic Hurricane Frequency under Twenty-First-Century Warming Conditions Thomas R. Knutson, et al. Nature Geoscience May 2008 Abstract Increasing sea surface temperatures in the tropical Atlantic Ocean and measures of Atlantic hurricane activity have been reported to be strongly correlated since at least 1950, raising concerns that future greenhouse-gas-induced warming6 could lead to pronounced increases in hurricane activity. Models that explicitly simulate hurricanes are needed to study the influence of warming ocean temperatures on Atlantic hurricane activity, complementing empirical approaches. Our regional climate model of the Atlantic basin reproduces the observed rise in hurricane counts between 1980 and 2006, along with much of the interannual variability, when forced with observed sea surface temperatures and atmospheric conditions7. Here we assess, in our model system, the changes in large-scale climate that are projected to occur by the end of the twenty-first century by an ensemble of global climate models, and find that Atlantic hurricane and tropical storm frequencies are reduced. At the same time, near-storm rainfall rates increase substantially. Our results do not support the notion of large increasing trends in either tropical storm or hurricane frequency driven by increases in atmospheric greenhouse-gas concentrations. Twentieth Century Antarctic Air Temperature and Snowfall Simulations by IPCC Climate Models A. J. Monaghan, et. al. Geophys. Res. Lett. 35 April 2008 Abstract We compare new observationally-based data sets of Antarctic near-surface air temperature and snowfall accumulation with 20th century simulations from global climate models (GCMs) that support the Intergovernmental Panel on Climate Change Fourth Assessment Report. Annual Antarctic snowfall accumulation trends in the GCMs agree with observations during 1960–1999, and the sensitivity of snowfall accumulation to near-surface air temperature fluctuations is approximately the same as observed, about 5% K−1. Thus if Antarctic temperatures rise as projected, snowfall increases may partially offset ice sheet mass loss by mitigating an additional 1 mm y−1 of global sea level rise by 2100. However, 20th century (1880–1999) annual Antarctic near-surface air temperature trends in the GCMs are about 2.5-to-5 times larger-than-observed, possibly due to the radiative impact of unrealistic increases in water vapor. Resolving the relative contributions of dynamic and radiative forcing on Antarctic temperature variability in GCMs will lead to more robust 21st century projections. » Climate Change: Science Articles

Policy Articles Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land Use Change Timothy Searchinger, et. al Science February 2008 Increasing production of biofuels in the United States leads to net increases in carbon emissions due to corresponding land use changes in the United States and worldwide. Abstract Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. Using a worldwide agricultural model to estimate emissions from land use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products. Land Clearing and the Biofuel Carbon Debt Joseph Fargione, et. al. Science February 2008 The clearing of carbon-rich land to grow biofuels creates a carbon debt larger than the short-term greenhouse gas emissions savings that come from consuming biofuels instead of fossil fuels. Abstract Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced. Converting rainforests, peatlands, savannas, or grasslands to produce food-based biofuels in Brazil, Southeast Asia, and the United States creates a ‘biofuel carbon debt’ by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions these biofuels provide by displacing fossil fuels. In contrast, biofuels made from waste biomass or from biomass grown on abandoned agricultural lands planted with perennials incur little or no carbon debt and offer immediate and sustained GHG advantages. What to Do About Climate Change Indur Goklany Policy Analysis February 2008 The world can best combat climate change and advance well-being by reducing present-day vulnerabilities to climate-sensitive problems that could be exacerbated by climate change rather than through GHG reductions. Summary Halting climate change would reduce cumulative mortality from various climate-sensitive threats, namely, hunger, malaria, and coastal flooding, by 4–10 percent in 2085, while increasing populations at risk from water stress and possibly worsening matters for biodiversity. But according to cost information from the UN Millennium Program and the IPCC, measures focused specifically on reducing vulnerability to these threats would reduce cumulative mortality from these risks by 50–75 percent at a fraction of the cost of reducing greenhouse gases (GHGs). Simultaneously, such measures would reduce major hurdles to the developing world’s sustainable economic development, the lack of which is why it is most vulnerable to climate change. In addition: Goklany's recent work on climate change appears in Mitigation and Adaption Strategies for Global Change and Energy & Environment. Those papers can be found at http://members.cox.net/igoklany/#cc. Failed Mechanism Barbara Haya International Rivers November 2007 The Kyoto Protocol's Clean Development Mechanism's subsidies of hydropower result in environmental destruction and are unlikely to create reductions in carbon emissions. Summary This report offers a critique of the Kyoto Protocol's Clean Development Mechanism (CDM), arguing that the subsidization of hydro technology projects works to hinder rather than help the Protocol's efforts against dangerous climate change. To Tax or Not to Tax: Alternative Approaches to Slowing Global Warming William D. Nordhaus Review of Environmental Economics and Policy "Price-type" controls like carbon taxes have various advantages over "quantity-type" controls like cap-and-trade. Abstract This study reviews different approaches to the political and economic control of global public goods such as global warming. It compares quantity-oriented control mechanisms like the Kyoto Protocol with price-type control mechanisms such as internationally harmonized carbon taxes. The analysis focuses on such issues as the relationship to ultimate targets, performance under conditions of uncertainty, volatility of induced carbon prices, the inefficiencies of taxation and regulation, potential for corruption and accounting finagling, and ease of implementation. It concludes that price-type approaches such as carbon taxes have major advantages for slowing global warming. » Climate Change: Policy Articles

Articles on Climate Change by AEI Scholars

Politics Posing as Science: A Preliminary Assessment of the IPCC's Latest Climate Change Report
by Kenneth P. Green, Joel Schwartz, and Steven F. Hayward

Time to Change U.S. Climate Policy
by Robert W. Hahn and Peter Passell

Green Jobs Created by Global Warming Initiatives
by Kenneth P. Green