Weather@home Climate Accountability: the causes of extreme heat in the Western US

This project aims to calculate the contribution of the world’s major carbon producers to climate change.

Over the past several years, scientists have succeeded in tracking with increasing confidence the portion of climate change that is tied directly to human activity, especially the burning of fossil fuels. Recently published research documents that nearly two-thirds of the industrial carbon pollution released into the atmosphere since 1854 can be directly traced to the carbon extracted from the Earth by just 90 entities – 83 producers of coal, oil and natural gas, and 7 cement manufacturers.

See recent publication: Tracing anthropogenic carbon dioxide and methane emissions to fossil fuel and cement producers, 1854-2010

Building on this research, the Union of Concerned Scientists is now collaborating with leading scientists who study climate change consequences at a regional scale and beyond. For the first time, this research will calculate the contribution of the world’s major carbon producers to climate change (such as increased average temperature, or increased number of days of extreme heat).

The California and Nevada heat wave of 2006, as well as the record-setting heat wave of late June 2013 in the Southwest were both deadly and costly for the local population. Recent research is able to attribute these types of events to climate change. The research shows that heat waves such as those in 2006 and 2013 in the Western U.S. were nearly 5 times more likely during the 2000s compared to the 1960s due to climate change.

We are now taking this research into extreme heat in the Western U.S. and combining it with the recent data on the major industrial carbon producers. Using a super-ensemble of regional climate model simulations from the experiment, we will determine how the carbon produced by these major industrial entities is contributing to the damages from climate change. In order to run the model simulations, we will rely on individual computers to download and run software from Using spare computing power of citizen scientists’ screen savers allows many runs of the models and increases the confidence in the results that UCS scientists and collaborators will analyze.

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More Information

The objective of this study is to assess the contribution of emissions sourced from major industrial carbon producers to regional scale climate impacts. We are designing this work to be catalytic – both to inform and motivate related research on other impacts and to inform strategies aimed at establishing accountability for climate change damages. This is now possible thanks to the recently published major carbon producers analysis by Richard Heede of the Climate Mitigation Service, Tracing anthropogenic carbon dioxide and methane emissions to fossil fuel and cement producers, 1854-2010.

The carbon entity data allows for the differentiation between carbon emissions, produced and marketed by each of the 90 major multi-national and state-owned coal, oil and gas companies (and their predecessors), and the total human attribution on climate change impacts. The carbon majors are defined as fossil fuel production entities and cement manufacturers that produced more than ≥8 million tonnes carbon per year (MtC/y), while the total human attribution case refers to all relevant human activities that have been measured and used in climate assessment model scenarios that influence climate change. The major carbon producers data can be applied to climate models to derive the carbon input’s effect on climate change impacts including global average temperature, sea level rise, and extreme events such as heat waves.

Trends in extreme events during the past decade constitute a facet of climate change that requires rigorous detection and attribution. These events are also more tangible to the general public than abstract statements of global average temperature since it affects their everyday lives. Events during the 2010-2012 time period had significant economic impact and were responsible for human casualties in many areas of the world. The Russian heat wave of 2010, for example, was unprecedented in scale, as were the concurrent floods in Pakistan and the subsequent floods in 2011. Devastating floods occurred with the Mississippi River in 2011, and this marked the start of a record-breaking year of droughts and heat waves in the United States that stretched into the fall of 2012, as well as the lowest level of ice extent in the Arctic. Some of the more severe events that recently captured the U.S. public’s attention included the Texas/Oklahoma heat wave and drought of the summer 2011 and Superstorm Sandy in October 2012.

Research during the past decade has shown that attribution to climate change can be analyzed by examining the risk or probability of extreme events (Stone et al. 2009). One of the methods championed by climate scientists is represented in the fraction of attributable risk [FAR (Allen, 2003; Stone and Allen 2005)], which assesses the attribution of climate anomalies to anthropogenic warming of the atmosphere. The main focus is to define the FAR by assessing the magnitude of an event such as the Texas/Oklahoma drought (Rupp et al., 2012) and the associated change in return period with carbon input from the major carbon producers analysis. An adequately-large ensemble of model runs would provide a distribution of possible severities of an extreme event in control runs and those forced with prescribed carbon emissions. Studies such as Otto et al. (2012) display how the numerical scale of the simulation numbers allows for clear separation between a climate with lower level of heat-trapping gases (1960s) and the recent period (2000s), such that the 2010 heat wave in western Russia was more likely to occur with the additional warming due to climate change (Figure 3).

Specifically, we are designing the research to assess the following questions:

  1. Is the major carbon producers signal large enough to be detected in the Western U.S. extreme heat model runs?
  2. Can we evaluate the results and compare with the Western Russia 2010 and Texas/Oklahoma 2011 heatwaves?
  3. Is the record-breaking heat over the United States during 2012 captured by simulations using the major carbon producers?


Allen, M. R. 2003: Liability for climate change, Nature, 421, 891–892.

Otto, F. E. L., N. Massey, G. J. van Oldenborgh, R. G. Jones, and M. R. Allen 2012: Reconciling two approaches to attribution of the 2010 Russian heat wave. Geophys. Res. Lett., 39,L04702, doi:10.1029/2011GL050422

Stone, D. A., and M. R. Allen 2005: Attribution of global surface warming without dynamical models, Geophys. Res. Lett., 32, L18711, doi:10.1029/2005GL023682.

Stone, D. A., M. R. Allen, P. A. Stott, P. Pall, S.-K. Min, T. Nozawa, and S. Yukimoto 2009: The Detection and Attribution of Human Influence on Climate. Annu. Rev. Environ. Resour. 2009. 34:1–16.

Rupp, D. E., P. W. Mote, N. Massey, C. J. Rye, R. Jones, M. R. Allen, 2012: Did human influence make the 2011 Texas drought more probable? In: Explaining Extreme Events in 2011 from a Climate Perspective. [T. C. Peterson, P. A. Stott and S. Herring, Editors] BAMS 1052-1054. BAMS-D-12-00021.