Claims Michael MacCracken, Chief Scientist for Climate Change Programs at the Climate Institute in Washington DC.
A wide range of scientific information makes clear that significant
global warming will result from unchecked human activities, particularly the combustion of coal, petroleum, and natural gas. The carbon dioxide (CO2) concentration is now over 37% above the pre-industrial value determined from air bubbles trapped in ice cores, and the methane (CH4) concentration is over 150% higher. That these higher concentrations will lead to global warming is clear from Earth’s history, from conditions on Mars and Venus, and from theoretical analyses. The changed concentrations are, however, not the only factors that affect climate. Both natural factors and other human activities (such as emission of sulfur dioxide and black carbon [soot], and changes in land cover) can also alter the climate. Actual conditions thus depend on the changing mix of these influences over time, all slowed by the time it takes for the oceans to warm, snow and ice to melt, and other factors to adjust.
While roughly similar situations in the geological past can serve as analogs, the present situation is unique in many ways. As a result, computer models of the climate’s atmosphere, oceans, land surface, and ice necessarily provide the best tools for understanding the potential response of the climate as forcings change. Because they are theoretical, however, testing is used to evaluate the level of confidence and caution to place in their results. The tests indicate that models do quite well in representing the range of climates around the world and its response to major volcanic eruptions. Most importantly, the models reproduce the large-scale space and time variations of the 20th century, finding that both natural and human-related factors played a role, with the human-related factors being the only way to explain global warming and climate change over the last several decades.
The really troublesome aspect of the model studies is that they tend to underestimate. Compared to model projections, Arctic sea ice is retreating faster, the Greenland and Antarctic ice sheets are losing mass faster, sea level is rising faster, oceans are taking up CO2 less rapidly, the ranges of plants and animals are shifting faster, and more. Closer examination has been showing that there are amplifying processes that have not yet been included in the models because it had been thought they would react slowly. Claims by skeptics that models overestimate and that recent warming has slowed rely on a very selective analysis of the data; they then draw a conclusion not backed by any of the other data sets indicating rapid change is underway.
For the future, increasing reliance on coal and other fossil fuels can only make the climate situation worse—and much worse if we do not rapidly start to reduce the global emissions exerting the strong warming influence. Both developed and developing nations have to participate in this effort, but issues of equity and alleviation of poverty merit thoughtful consideration, as described in the 1992 UN Framework Convention on Climate Change. Fortunately, the science of the situation suggests an approach of ‘Differentiated Responsibilities, but Comparable Challenges’ that can accomplish this.
A wide range of scientific information makes clear that significant
global warming will result from unchecked human activities, particularly the combustion of coal, petroleum, and natural gas. The carbon dioxide (CO2) concentration is now over 37% above the pre-industrial value determined from air bubbles trapped in ice cores, and the methane (CH4) concentration is over 150% higher. That these higher concentrations will lead to global warming is clear from Earth’s history, from conditions on Mars and Venus, and from theoretical analyses. The changed concentrations are, however, not the only factors that affect climate. Both natural factors and other human activities (such as emission of sulfur dioxide and black carbon [soot], and changes in land cover) can also alter the climate. Actual conditions thus depend on the changing mix of these influences over time, all slowed by the time it takes for the oceans to warm, snow and ice to melt, and other factors to adjust.While roughly similar situations in the geological past can serve as analogs, the present situation is unique in many ways. As a result, computer models of the climate’s atmosphere, oceans, land surface, and ice necessarily provide the best tools for understanding the potential response of the climate as forcings change. Because they are theoretical, however, testing is used to evaluate the level of confidence and caution to place in their results. The tests indicate that models do quite well in representing the range of climates around the world and its response to major volcanic eruptions. Most importantly, the models reproduce the large-scale space and time variations of the 20th century, finding that both natural and human-related factors played a role, with the human-related factors being the only way to explain global warming and climate change over the last several decades.
The really troublesome aspect of the model studies is that they tend to underestimate. Compared to model projections, Arctic sea ice is retreating faster, the Greenland and Antarctic ice sheets are losing mass faster, sea level is rising faster, oceans are taking up CO2 less rapidly, the ranges of plants and animals are shifting faster, and more. Closer examination has been showing that there are amplifying processes that have not yet been included in the models because it had been thought they would react slowly. Claims by skeptics that models overestimate and that recent warming has slowed rely on a very selective analysis of the data; they then draw a conclusion not backed by any of the other data sets indicating rapid change is underway.
For the future, increasing reliance on coal and other fossil fuels can only make the climate situation worse—and much worse if we do not rapidly start to reduce the global emissions exerting the strong warming influence. Both developed and developing nations have to participate in this effort, but issues of equity and alleviation of poverty merit thoughtful consideration, as described in the 1992 UN Framework Convention on Climate Change. Fortunately, the science of the situation suggests an approach of ‘Differentiated Responsibilities, but Comparable Challenges’ that can accomplish this.
