Frozen
What Scientists Know Is Not a Function of What Scientists Know
P.D. Magnus
Philosophy of Science, December 2013, Pages 840-849
Abstract:
There are two senses of ‘what scientists know’: An individual sense (the separate opinions of individual scientists) and a collective sense (the state of the discipline). The latter is what matters for policy and planning, but it is not something that can be directly observed or reported. A function can be defined to map individual judgments onto an aggregate judgment. I argue that such a function cannot effectively capture community opinion, especially in cases that matter to us.
----------------------
Special Interests and the Media: Theory and an Application to Climate Change
Jesse Shapiro
NBER Working Paper, January 2014
Abstract:
I present a model in which competing special interests seek policy influence through the news media. In the model a journalist reports on expert opinion to a voter. Two competing interested parties can invest to acquire credentialed advocates to represent their positions in the press. Because advocates are easier to obtain when expert opinion is divided, the activities of special interests can reveal useful information to the voter. However, competition among special interests can also reduce the amount of information communicated to the voter, especially on issues with large economic stakes and a high likelihood of a scientific consensus. The model provides an account of persistent voter ignorance on climate change and other high-stakes scientific topics.
----------------------
Sensitivity of collective action to uncertainty about climate tipping points
Scott Barrett & Astrid Dannenberg
Nature Climate Change, January 2014, Pages 36–39
Abstract:
Despite more than two decades of diplomatic effort, concentrations of greenhouse gases continue to trend upwards, creating the risk that we may someday cross a threshold for ‘dangerous’ climate change. Although climate thresholds are very uncertain, new research is trying to devise ‘early warning signals’ of an approaching tipping point. This research offers a tantalizing promise: whereas collective action fails when threshold uncertainty is large, reductions in this uncertainty may bring about the behavioural change needed to avert a climate ‘catastrophe’. Here we present the results of an experiment, rooted in a game-theoretic model, showing that behaviour differs markedly either side of a dividing line for threshold uncertainty. On one side of the dividing line, where threshold uncertainty is relatively large, free riding proves irresistible and trust illusive, making it virtually inevitable that the tipping point will be crossed. On the other side, where threshold uncertainty is small, the incentive to coordinate is strong and trust more robust, often leading the players to avoid crossing the tipping point. Our results show that uncertainty must be reduced to this ‘good’ side of the dividing line to stimulate the behavioural shift needed to avoid ‘dangerous’ climate change.
----------------------
Long-term climate policy implications of phasing out fossil fuel subsidies
Valeria Jana Schwanitz et al.
Energy Policy, forthcoming
Abstract:
It is often argued that fossil fuel subsidies hamper the transition towards a sustainable energy supply as they incentivize wasteful consumption. We assess implications of a subsidy phase-out for the mitigation of climate change and the low-carbon transformation of the energy system, using the global energy–economy model REMIND. We compare our results with those obtained by the International Energy Agency (based on the World Energy Model) and by the Organization for Economic Co-Operation and Development (OECD-Model ENV-Linkages), providing the long-term perspective of an intertemporal optimization model. The results are analyzed in the two dimensions of subsidy phase-out and climate policy scenarios. We confirm short-term benefits of phasing-out fossil fuel subsidies as found in prior studies. However, these benefits are only sustained to a small extent in the long term, if dedicated climate policies are weak or nonexistent. Most remarkably we find that a removal of fossil fuel subsidies, if not complemented by other policies, can slow down a global transition towards a renewable based energy system. The reason is that world market prices for fossil fuels may drop due to a removal of subsidies. Thus, low carbon alternatives would encounter comparative disadvantages.
----------------------
The Cost of Carbon Dioxide Abatement from State Renewable Portfolio Standards
Erik Johnson
Resource and Energy Economics, forthcoming
Abstract:
Renewable Portfolio Standards (RPSs) have become a popular tool for state governments to promote renewable electricity generation and to decrease carbon dioxide emissions within a state or region. Renewable portfolio standards are a policy tool likely to persist for many decades due to the long term goals of many state RPSs and the likely creation of a federal RPS alongside any comprehensive climate change bill. Even though RPSs have become a popular policy tool, there is little empirical evidence about their costs. Using the temporal and regional variation in RPS requirements, I estimate the long-run price elasticity of supply of renewable electricity generation to be 2.67 (95% CI of 1.74, 3.60). Using my preferred elasticity estimate, I calculate the marginal cost of abatement from RPSs is at least $11 per ton of CO2 compared to a marginal cost of abatement of $3 per ton in the Regional Greenhouse Gas Initiative.
----------------------
A. Spence et al.
Journal of Environmental Psychology, June 2014, Pages 17–28
Abstract:
Reducing energy use is key in meeting ambitious climate change targets being set around the world. This research considers the psychological impact, and potential for behavioural spillover, resulting from receiving energy information framed in terms of financial costs or the environment. We utilised an online tool in order to present undergraduate participants with an energy display simulation of their own energy use and presented energy use in terms of kilowatt-hours, carbon dioxide (CO2), or costs. Study 1 found increased motivations to save energy for climate change reasons and some indications that environmental behaviour might increase after participants received CO2 information compared to alternatives. Study 2 found that CO2 information increased climate change salience, which mediated effects observed on environmental behaviour intentions. Data suggest that highlighting climate change in relation to energy savings may be useful for promoting broader environmental behaviour.
----------------------
Increasing frequency of extreme El Niño events due to greenhouse warming
Wenju Cai et al.
Nature Climate Change, forthcoming
Abstract:
El Niño events are a prominent feature of climate variability with global climatic impacts. The 1997/98 episode, often referred to as ‘the climate event of the twentieth century’, and the 1982/83 extreme El Niño, featured a pronounced eastward extension of the west Pacific warm pool and development of atmospheric convection, and hence a huge rainfall increase, in the usually cold and dry equatorial eastern Pacific. Such a massive reorganization of atmospheric convection, which we define as an extreme El Niño, severely disrupted global weather patterns, affecting ecosystems, agriculture, tropical cyclones, drought, bushfires, floods and other extreme weather events worldwide. Potential future changes in such extreme El Niño occurrences could have profound socio-economic consequences. Here we present climate modelling evidence for a doubling in the occurrences in the future in response to greenhouse warming. We estimate the change by aggregating results from climate models in the Coupled Model Intercomparison Project phases 3 (CMIP3) and 5 (CMIP5) multi-model databases, and a perturbed physics ensemble. The increased frequency arises from a projected surface warming over the eastern equatorial Pacific that occurs faster than in the surrounding ocean waters, facilitating more occurrences of atmospheric convection in the eastern equatorial region.
----------------------
Diana Lane et al.
PLoS ONE, December 2013
Abstract:
The biological and economic values of coral reefs are highly vulnerable to increasing atmospheric and ocean carbon dioxide concentrations. We applied the COMBO simulation model (COral Mortality and Bleaching Output) to three major U.S. locations for shallow water reefs: South Florida, Puerto Rico, and Hawaii. We compared estimates of future coral cover from 2000 to 2100 for a “business as usual” (BAU) greenhouse gas (GHG) emissions scenario with a GHG mitigation policy scenario involving full international participation in reducing GHG emissions. We also calculated the economic value of changes in coral cover using a benefit transfer approach based on published studies of consumers' recreational values for snorkeling and diving on coral reefs as well as existence values for coral reefs. Our results suggest that a reduced emissions scenario would provide a large benefit to shallow water reefs in Hawaii by delaying or avoiding potential future bleaching events. For Hawaii, reducing emissions is projected to result in an estimated “avoided loss” from 2000 to 2100 of approximately $10.6 billion in recreational use values compared to a BAU scenario. However, reducing emissions is projected to provide only a minor economic benefit in Puerto Rico and South Florida, where sea-surface temperatures are already close to bleaching thresholds and coral cover is projected to drop well below 5% cover under both scenarios by 2050, and below 1% cover under both scenarios by 2100.
----------------------
Stephen Vavrus & Ruben Behnke
International Journal of Climatology, forthcoming
Abstract:
Motivated by the documented linkage between water-borne disease outbreaks and heavy rainfall, we compare simulations of precipitation in Wisconsin from two different downscaling procedures (statistical and dynamical) and global climate models (GCMs) for the late 20th and middle 21st centuries (SRES A2 greenhouse emissions scenario). In the inter-model mean, all the three methods produce reasonably accurate simulations of seasonal and annual precipitation amounts during the historical period of 1971–2000 (yearly biases <5%), but the GCMs severely underestimate extreme precipitation compared with downscaled output and observations. The modelling methodologies agree that Wisconsin should experience a modestly wetter future climate (annual increase <10%) by the middle 21st century (2041–2070), comprised of more precipitation during winter, spring, and autumn but an equivocal summertime signal. The future simulations also exhibit robust increases in the frequency and intensity of extreme daily precipitation, consisting of larger relative changes in the return periods of heavy events (up to −50%) than in the accumulations (<30%). Although the modelling procedures vary substantially in their projected absolute differences in future precipitation, they agree surprisingly well on the simulated relative differences (percent change) of both mean and extreme precipitation. Unfortunately, there is little consistency in the simulated spatial patterns of future precipitation change across Wisconsin, complicating societal adaptation measures to enhanced extremes. Nevertheless, the composite projections presented here suggest that impending hydrological changes in Wisconsin represent a public health threat, by virtue of increasingly extreme precipitation promoting water-borne disease outbreaks.
----------------------
Less Reliable Water Availability in the 21st Century Climate Projections
Sanjiv Kumar et al.
Earth's Future, forthcoming
Abstract:
The temporal variability of river and soil water affects society at time scales ranging from hourly to decadal. The available water (AW), i.e. precipitation minus evapotranspiration, represents the total water available for runoff, soil water storage change and ground water recharge. The reliability of AW is defined as the annual range of AW between local wet and dry seasons. A smaller annual range represents greater reliability and a larger range denotes less reliability. Here we assess the reliability of AW in the 21st century climate projections by 20 climate models from phase 5 of the Coupled Model Inter-comparison Project (CMIP5). The multi-model consensus suggests less reliable AW in the 21st century than the 20th century with generally decreasing AW in local dry seasons and increasing AW in local wet seasons. In addition to the canonical perspective from climate models that wet regions will get wetter, this study suggests greater dryness during dry seasons even in regions where the mean climate becomes wetter. Lower emission scenarios show significant advantages in terms of minimizing impacts on AW, but do not eliminate these impacts altogether.
----------------------
Differences among OECD countries’ GHG emissions: Causes and policy implications
K.S. Calbick & Thomas Gunton
Energy Policy, forthcoming
Abstract:
This article assesses the reasons for observed differences in greenhouse gas (GHG) emissions among high-income OECD countries. Nine factors were tested: climate, population pressure (measured as both growth and density), economic output per capita, technological development, industrial structure, energy prices, environmental governance, pollution abatement and control expenditures, and environmental pricing. Based on a series of regression analyses, three factors – energy prices, economic output per capita, and environmental governance – were identified as the most important factors for explaining differences in OECD per capita GHG emissions. Combined, these three factors explain about 81% of the variation observed in OECD per capita GHG emissions. Individually, energy prices explains about 55% of the variation in per capita GHG emissions, while economic output per capita explains about 19%, and environmental governance about 7%. These findings show that behavioural choices based on existing technologies, rather than exogenous factors such as climate, determine differences in GHG emissions and, therefore, policy options to change behaviour such as increasing energy prices and other regulatory changes have the potential to significantly reduce GHG emissions.
----------------------
Historical trends in greenhouse gas emissions of the Alberta oil sands (1970–2010)
Jacob Englander, Sharad Bharadwaj & Adam Brandt
Environmental Research Letters, November 2013
Abstract:
There has been increased scrutiny of the Alberta oil sands due to their high carbon intensity (CI) relative to conventional crude oil. Relying entirely on public and peer-reviewed data sources, we examine historical trends in the CI of oil sands extraction, upgrading, and refining. Monthly data were collected and interpolated from 1970 to 2010 (inclusive) for each oil sands project. Results show a reduction in oil sands CI over time, with industry-average full-fuel cycle (well-to-wheels, WTW) CI declining from 165 gCO2e MJ−1 higher heating value (HHV) of reformulated gasoline (RFG) to 105 (−12, +9) gCO2e MJ−1 HHV RFG. 2010 averages by production pathways are 102 gCO2e MJ−1 for Mining and 111 gCO2e MJ−1 for in situ. The CI of mining-based projects has declined due to upgrader efficiency improvements and a shift away from coke to natural gas as a process fuel. In situ projects have benefitted from substantial reductions in fugitive emissions from bitumen batteries. Both mining and in situ projects have benefitted from improved refining efficiencies. However, despite these improvements, the CI of oil sands production (on a pathway-average basis) ranges from 12 to 24% higher than CI values from conventional oil production. Due to growing output, total emissions from the oil sands continue to increase despite improved efficiency: total upstream emissions were roughly 65 MtCO2e in 2010, or 9% of Canada's emissions.
----------------------
J.A. de Gouw et al.
Earth's Future, forthcoming
Abstract:
Since 1997, an increasing fraction of electric power in the U.S. has been generated from natural gas. Here, we use data from continuous emissions monitoring systems (CEMS), which measure emissions at the stack of most U.S. electric power generation units, to investigate how this switch affected the emissions of CO2, NOx and SO2. Per unit of energy produced, natural gas power plants equipped with combined cycle technology emit on average 44% of the CO2 compared with coal power plants. As a result of the increased use of natural gas, CO2 emissions from U.S. fossil-fuel power plants were 23% lower in 2012 than they would have been, if coal had continued to provide the same fraction of electric power as in 1997. In addition, natural gas power plants with combined cycle technology emit less NOx and far less SO2 per unit energy produced than coal power plants. The increased use of natural gas has therefore led to emissions reductions of NOx (40%) and SO2 (44%), in addition to those obtained from the implementation of emissions control systems on coal power plants. These benefits to air quality and climate should be weighed against the increase in emissions of methane, volatile organic compounds and other trace gases that are associated with the production, processing, storage and transport of natural gas.
----------------------
Small influence of solar variability on climate over the past millennium
Andrew Schurer, Simon Tett & Gabriele Hegerl
Nature Geoscience, forthcoming
Abstract:
The climate of the past millennium was marked by substantial decadal and centennial scale variability in the Northern Hemisphere. Low solar activity has been linked to cooling during the Little Ice Age (AD 1450–1850) and there may have been solar forcing of regional warmth during the Medieval Climate Anomaly (AD 950–1250). The amplitude of the associated changes is, however, poorly constrained, with estimates of solar forcing spanning almost an order of magnitude. Numerical simulations tentatively indicate that a small amplitude best agrees with available temperature reconstructions. Here we compare the climatic fingerprints of high and low solar forcing derived from model simulations with an ensemble of surface air temperature reconstructions for the past millennium. Our methodology also accounts for internal climate variability and other external drivers such as volcanic eruptions, as well as uncertainties in the proxy reconstructions and model output. We find that neither a high magnitude of solar forcing nor a strong climate effect of that forcing agree with the temperature reconstructions. We instead conclude that solar forcing probably had a minor effect on Northern Hemisphere climate over the past 1,000 years, while, volcanic eruptions and changes in greenhouse gas concentrations seem to be the most important influence over this period.
----------------------
Future Arctic Climate Changes: Adaptation and Mitigation Timescales
James Overland et al.
Earth's Future, forthcoming
Abstract:
The climate in the Arctic is changing faster than in mid-latitudes. This is shown by increased temperatures, loss of summer sea ice, earlier snow melt, impacts on ecosystems, and increased economic access. Arctic sea ice volume has decreased by 75 % since the 1980s. Long-lasting global anthropogenic forcing from CO2 has increased over the previous decades and is anticipated to increase over the next decades. Temperature increases in response to greenhouse gases are amplified in the Arctic through feedback processes associated with shifts in albedo, ocean and land heat storage, and near-surface longwave radiation fluxes. Thus for the next few decades out to 2040, continuing environmental changes in the Arctic are very likely, and the appropriate response is to plan for adaptation to these changes. For example, it is very likely that the Arctic Ocean will become nearly seasonally sea ice free before 2050 and possibly within a decade or two, which in turn will further increase Arctic temperatures, economic access, and ecological shifts. Mitigation becomes an important option to reduce potential Arctic impacts in the second half of the 21st century. Using the most recent set of climate model projections (CMIP5), multi-model mean temperature projections show an Arctic-wide end of century increase of +13 ° C in late fall and +5 ° C in late spring for a business as usual emission scenario (RCP8.5) in contrast to +7 ° C in late fall and + 3° C in late spring if civilization follows a mitigation scenario (RCP4.5). Such temperature increases demonstrate the heightened sensitivity of the Arctic to greenhouse gas forcing.
----------------------
Weakened tropical circulation and reduced precipitation in response to geoengineering
Angus Ferraro, Eleanor Highwood & Andrew Charlton-Perez
Environmental Research Letters, January 2014
Abstract:
Geoengineering by injection of reflective aerosols into the stratosphere has been proposed as a way to counteract the warming effect of greenhouse gases by reducing the intensity of solar radiation reaching the surface. Here, climate model simulations are used to examine the effect of geoengineering on the tropical overturning circulation. The strength of the circulation is related to the atmospheric static stability and has implications for tropical rainfall. The tropical circulation is projected to weaken under anthropogenic global warming. Geoengineering with stratospheric sulfate aerosol does not mitigate this weakening of the circulation. This response is due to a fast adjustment of the troposphere to radiative heating from the aerosol layer. This effect is not captured when geoengineering is modelled as a reduction in total solar irradiance, suggesting caution is required when interpreting model results from solar dimming experiments as analogues for stratospheric aerosol geoengineering.
----------------------
Changes in Seasonal Predictability due to Global Warming
Timothy DelSole et al.
Journal of Climate, January 2014, Pages 300–311
Abstract:
The change in predictability of monthly mean temperature in a future climate is quantified based on the Community Climate System Model, version 4. According to this model, the North Atlantic overtakes the El Niño–Southern Oscillation (ENSO) as the dominant area of seasonal predictability by 2095. This change arises partly because ENSO becomes less variable and partly because the ENSO teleconnection pattern expands into the Atlantic. Over land, the largest change in temperature predictability occurs in the tropics and is predominantly due to a decrease in ENSO variability. The southern peninsula of Africa and northeast South America are predicted to experience significant drying in a future climate, which decreases the effective heat capacity and memory, and hence increases variance independently of ENSO changes. Extratropical land areas experience enhanced precipitation in a future climate, which decreases temperature variance by the same mechanism. Finally, the model predicts that surface temperatures near the poles will become more predictable and less variable in a future climate, primarily because melting sea ice exposes the underlying sea surface temperature, which is more predictable owing to its longer time scale. Some of these results, especially the change in ENSO variance, are known to be model dependent. This paper also advances the use of information theory to quantify predictability, including 1) deriving a quantitative relation between predictability of the first and second kinds; 2) showing how differences in predictability can be decomposed in two dramatically different ways, facilitating physical interpretation; and 3) proposing a sample estimate of mutual information whose significance can be tested using standard techniques.