The Importance of Climate Change

ONE grand challenge facing the international scientific community is determining the record of the Earth's climate since the last ice age and assessing whether humans have significantly impacted the climate in recent years. If we conclude with confidence that human activities do indeed affect climate and that the consequences pose real dangers, responding to such dangers will present tremendous political and economic challenges to every nation. Working on such a problem is a worthy mission for a national laboratory; Livermore's multidisciplinary expertise enables us to contribute substantive solutions.
Our understanding of climate variability has increased greatly over the past few decades because the record of climate since the last glaciation has been developed through studying sediments from melting episodes in ice sheets and ice caps, and pollen, dust, and isotopic records in ice caps and lake and river sediments. We have come to appreciate that we live in a system that has experienced great temperature and precipitation swings in the recent millennia.
A consequence of this insight is that interpreting global warming in simple terms such as an average warming of a fraction of a degree Celsius over the Earth's surface could greatly underestimate the actual effects. Change will have a regional pattern, causing warming in some regions and cooling in others, as global patterns of precipitation and other atmospheric variables shift. In particular, any perturbation of the ocean currents that make up the thermohaline cycle (believed to be stable for the past several thousand years) could produce dramatic regional thermal effects such as cooling Europe by several degrees Celsius and drying the center of the North American continent.
We know from both the historical and archaeological records about events such as the Little Ice Age in Europe and hundred-year droughts in North and South America. If our actions produce similar climate change, the human consequences-ecological, political, and economic-could rival any natural disaster in human record. But before worrying too much about disasters, we must have more information.
The attribution of climate change to human activities, coupled with increasing confidence (now not available) in the ability to predict the effects of climate change, will lead to the need to evaluate the options, costs, and credibility of measures to mitigate the effects of such change. This evaluation will require an unprecedented combination of scientific, economic, and policy skills to reassure the political system if the consensus required to modify the economies of the developed world and the path of the developing world is to be achieved. Unprecedented confidence in the reliability of scientific assessments will be necessary.
The work described in this issue beginning on p. 6 summarizes several LLNL research projects that have advanced our understanding of the climatic consequences of human activities and increased our confidence to detect climate change and determine if it is linked to humans. We have shown that the burning of fossil fuel that increases atmospheric carbon dioxide and causes warming globally also injects sulfate aerosols that promote local cooling. This knowledge makes it possible to predict patterns of global warming and cooling from signatures that are associated with human activities.
In developing tools for testing climate models, we have statistically compared the past climate record with predictions based on fossil fuel consumption records. We found remarkably suggestive agreement in the geographic patterns of warming and cooling. While these results are currently the subject of controversy regarding the evaluation processes of the Intergovernmental Panel on Climate Change, there is strong consensus within the scientific community that the data suggest a human origin for the global warming that is currently being observed.
Livermore's strengths and role in climate studies come from several capabilities. We are conducting an international program to create standard data records and methodologies to test the credibility of climate models. Our scientists study inadequately characterized mechanisms of climate such as atmospheric chemistry, aerosol, and radiation effects, and they develop models that allow realistic coupling of atmospheric and ocean processes. Modeling activities grow with collaborations such as the Accelerated Strategic Computing Initiative (ASCI), which links us to new computational capabilities within the Department of Energy. Measurements of the carbon-14 record of the modern carbon cycle and the isotopic records of the paleoclimate are provided by projects conducted at our Center for Accelerator Mass Spectrometry.
Together, our powerful computational, modeling, and measurement capabilities give us the confidence that Lawrence Livermore will continue to play a major role in responding to this critical scientific challenge.
Jay C. Davis is the Associate Director for Environmental Programs.

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