The IPCC 2007 report Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.
11 of the past 12 years are the warmest since reliable records began around 1850
Global warming is "very likely" caused by man, meaning more than 90 percent certain. That's the strongest expression of certainty to date from the panel. If carbon dioxide concentrations in the atmosphere reach twice their pre-industrial levels, the report said, the global climate will probably warm by 3.5 to 8 degrees. But there would be more than a 1-in-10 chance of much greater warming, a situation many earth scientists say poses an unacceptable risk.
A snow-maker created snow on the slopes of Parsenn in Davos, Switzerland in February. Many attribute this winter's low snowfall to global warming.
But if the world does get greenhouse gas emissions under control _ something scientists say they hope can be done _ the best estimate is about 3 degrees Fahrenheit.
Sea levels are projected to rise 7 to 23 inches by the end of the century. Add another 4 to 8 inches if recent, surprising melting of polar ice sheets continues. Sea level rise could get worse after that. By 2100, if nothing is done to curb emissions, the melting of Greenland's ice sheet would be inevitable and the world's seas would eventually rise by more than 20 feet, Bindoff said.
That amount of sea rise would take centuries, said Andrew Weaver of the University of Victoria in Canada, but 'if you're in Florida or Louisiana, or much of western Europe or southeast Asia or Bangladesh... or Manhattan... you don't want that,' he said.
The debate over whether global warming is happening and that it is anthropogenic is over (fierce resistance from petroleum companies is now past) but now the debate is “what does it cost to reduce carbon emissions to certain levels that will prevent the worst harm?)
The Stern Report-2006 The economic model used in the Stern Review finds that the damages from business as usual would be expected to reduce GDP by 5% based on market impacts alone, or 11% including a rough estimate for the value of health and environmental effects that do not have market prices (“externalities,” in the jargon of economics). If the sensitivity of climate to CO2 levels turns out to be higher than the baseline estimates, these losses could rise to 7% and more than 14%, respectively. A disaggregated description of impacts by sector and region is generally in agreement with these numbers, according to the Review. Stern speculates that an adjustment for equity weighting, reflecting the fact that the impacts will fall most heavily on poor countries, could lead to losses valued at 20% of global GDP. These figures are substantially greater than the comparable estimates from most economists
These damages can be largely avoided, at much lower cost, through emissions reduction (or “mitigation,” in the jargon of climate change). Stabilization at 500–550 parts per million (ppm) of CO2-equivalent7 in the atmosphere would avoid most, though not all, of the “business as usual” damages. Both direct estimates of mitigation costs and a review of results from many different models suggest that stabilization at this level would cost about 1% of GDP. Stabilization below 450 ppm, according to Stern, is no longer feasible
First, what is the maximum atmospheric concentration of CO2 at which unacceptable climate outcomes can be ruled out with a high degree of confidence? Second, what is the least-cost strategy for stabilizing at that concentration? The first question is the essence of a precautionary approach to policy, in a context of complex and uncertain scientific information. It involves several difficult, but not impossible judgments: about the (probabilistic) link between CO2 levels and climate outcomes; about which climate outcomes are unacceptable; and about how high a degree of confidence is required that we can avoid those outcomes.
What To Do? Adaptation-Favorite argument of neoclassical economists. They believe that large uncertainties in climate projections make it unwise to spend large sums trying to avert outcomes that may never materialize. They believe that human systems can adapt to climate change much faster than they occur. They maintain that while doubling of CO2 will take place over the next century, financial markets adapt in minutes, labor markets in several years, and the planning horizon for significant economic and technological change is at most two or three decades. But what are the risks of “large, abrupt, and unwelcome shifts in climate?”
Mitigation “curtailing the greenhouse gas buildup to prevent, minimize, or at least slow global warming” (harper, p. 97) White surfaces and vegetation. Residential water heating. Residential space heating Residential and commercial lighting. Industrial energy management Fuel efficiency
Transportation Energy Management Vehicle efficiency Alternative fuels (ethanol from biomass, solar-hydrogen) Transportation demand management Electricity and fuel supply
Carbon Tax? tax on energy sources which emit carbon dioxide into the atmosphere. It is an example of a pollution tax, which some economists favor because they tax a "bad" rather than a "good" (such as income). Because a carbon tax addresses a negative externality
Equity issue that Harper raises (p. 101) the regressivity of a carbon tax could be minimized or eliminated by allocating the tax revenues to benefit the less affluent. Wealthier households use more energy, on average — they drive and fly more, have bigger (and sometimes multiple) houses, and buy more products that require energy to manufacture and use. Most carbon tax revenues will therefore come from families of above-average means, as well as corporations and government. This creates a basis for progressive tax-shifting: transferring a portion of the tax burden from regressive taxes such as the payroll tax (at the federal level) and the sales tax (at the state level) onto pollution and pollution-generating activities. Another progressive approach in the United States is to rebate the carbon tax revenues equally to all U.S. residents — a national version of the Alaska Permanent Fund, which once a year sends identical checks to all state residents from the state’s North Slope oil royalties. Because income and energy consumption are strongly correlated, most poorer households would get more back in rebates or tax savings than they would pay in the carbon tax.