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The evidence is clear 

Human activity has caused global climate change.

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The clear scientific evidence that man-induced climate change could have profound and perhaps disastrous consequences is being denied by economic and political forces. In the U.S., those with the most to lose, such as the coal and oil industries, are funding efforts to discredit the scientific basis for climate change concerns. Science is not a take-it-or-leave-it proposition. Gravity, light, and other forces act with or without agreement about the science of how they operate.

 The scientific knowledge of how gases can insulate a planet’s surface has been understood for longer than a century. In 1824, the brilliant mathematician Joseph Fourier postulated the ability of atmospheric gases to act as an insulator for a planet. In 1896, Svante Arrhenius, a Nobel laureate, developed the equations that are used to calculate the insulating effect of various gases. The Intergovernmental Panel on Climate Change (IPCC) has researched and reported on Earth’s warming since the late 1980s. IPCC reports are a consensus of current knowledge from more than 600 eminent scientists. IPCC has produced four formal reports and was awarded the Nobel Peace Prize in 2007 for this work. (Read these reports on the Internet).

 Water vapor and carbon dioxide (CO2) are the primary greenhouse gases. Global water vapor is relatively constant, but atmospheric CO2 has increased from about 280 ppm in 1750 to 389 ppm today (June 2009; see Swanson, Atmospheric CO2 levels are now higher than at any time in the last 800,000 years. This rapid buildup caused by widespread use of fossil fuels is responsible for approximately 90 percent of human-caused planetary warming. Other activities, such as the human deforestation of about half the planet, have reduced natural CO2 absorption while releasing methane, another powerful greenhouse gas.

 For the last 10,000 years various terrestrial and marine systems have kept the Earth’s average temperature and precipitation in a narrow range. This stable climate allowed the development of agriculture and increased human population. The scientific discovery of microbes led to public health and medical advances, which, along with improved agriculture, has allowed human population to increase from about 1.2 billion in 1850 to about 6.9 billion today. As the world modernizes, the primary driver of atmospheric CO2 increase is fossil fuel combustion. Burning fossil fuels (coal, oil, natural gas) releases into the atmosphere carbon that was buried in the Earth millenia ago. Atmospheric levels of methane and nitrous oxide are also increasing from human activities (for example, applying chemical fertilizers). The CIA Fact Book estimates world population growth at 220,980 people every day in 2009. The CIA forecasts human population increasing to nine billion in the next three to four decades. Clearly, nature is under strain to absorb all these people and their fossil fuel combustion, and something will inevitably give.

 Is climate change already happening? According to the Pew Center, “Over the past 50 years, the [worldwide] data on extreme temperatures have shown similar trends of rising temperatures: cold days, cold nights, and frosts occurred less frequently over time, while hot days, hot nights, and heat waves occurred more frequently.” This is now causing sea-level rise, mountain glaciers to disappear, and rapid change in ocean currents, such as the Gulf Stream. The ocean has also become about 30 percent more acidic as it absorbs CO2 from the atmosphere (US EPA). Australia now experiences what is ahead for much of the world. “Drought, fires, killer heat waves, wildlife extinction and mosquito-borne illness—the things that climate change models are predicting—have already arrived,” say Australian scientists (Los Angeles Times 2008). Deserts across Asia, Africa, and the Indian sub-continent are also expanding substantially, causing dislocation and contributing to civil wars (e. g., Sudan).

 U.S. military planners are taking the threat of climate change very seriously. The think tank CNA is a nonpartisan research organization that operates the Center for Naval Analyses and the Institute for Public Research. A recent CNA report reviewed how likely climate change impacts might affect US military commitments (and taxpayer expenses, I might add). In the report summary, retired Admiral T. Joseph Lopez, who commanded peacekeeping forces in Bosnia, said, “The impacts of climate change will be huge — deserts move north, coastal areas threatened, the dislocation of people. I’m a student of instability, and instability is the enemy. It helps religious extremists and terrorists,” (Seattle Times, 2008). The CNA report concludes,“We will pay for this one way or another. We will pay to reduce greenhouse gas emissions today, and we’ll have to take an economic hit of some kind. Or, we will pay the price later in military terms. And that will involve human lives. There will be a human toll.”—Gen Zinni.

 The science is clear and the time for talk is running out. We cannot continue using the atmosphere as a sewer without substantial human and financial costs, and perhaps drastic and irreversible consequences.

 Dave Morrow is a local atmospheric scientist with more than 30 years experience in the field. He has worked for the U.S. EPA, state and local government agencies, and private clients including the American Petroleum Institute. His most notable achievement is educating Caltrans about automated vehicle identification, that is now used to pay tolls on all Bay Area bridges, with resultant congestion and air emission reductions. Send comments via the editor at



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