Addressing Climate Change For Our Grandchildren
Fifteen years ago the Intergovernmental Panel on Climate Change (IPCC) submitted to governments its first assessment of the science of climate change. It drew upon a long history of climate science going back several hundred years, as well as research coordinated through the World Climate Research Program, sponsored by the International Council for Science, the World Meteorological Organization and the Intergovernmental Oceanographic Commission of UNESCO.
I was then chair of the international scientific committee for the World Climate Research Program (WCRP). The IPCC concluded that it was not possible to say whether human activities were already changing the climate. However, the assessment clearly identified that climate would change in significant ways over the next century unless there were major reductions in greenhouse gas emissions from human activities.
On this basis, most countries agreed at the 1992 Earth Summit to the United Nations Framework Convention on Climate Change (UNFCCC). Five years later, the IPCC's second assessment was the basis for the decision at the Second Conference of the Parties in Geneva that the science was adequate for negotiations a year later in Kyoto. The new science included the first agreement that "The balance of evidence suggests that there is a discernible human influence on global climate."
In 2001, the IPCC's third assessment was more conclusive: "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities." This firmer statement had a role in some countries' decision to ratify the Kyoto Protocol.
Important but difficult considerations for policy makers are the long time scales of the climate system, long with respect to normal political time scales. Although water cycles through the atmosphere in about 10 days, removing aerosol and other pollutants as it does so, the time scales of the main two greenhouse gases under the Protocol, carbon dioxide and methane, are much longer. When we emit these gases into the atmosphere, they mix around the globe in a few years.
This makes it a global problem - it does not matter, from the climate's perspective, where the gases came from. And, once in the atmosphere, they stay there for about a decade for methane and a century for carbon dioxide. The climate system and sea level take even longer to adjust.
This means that we are reducing greenhouse gas emissions now to have positive impacts in decades from now; even after we stabilize the atmospheric concentrations, the climate will continue to warm and the sea level rise for decades to centuries longer.
We are addressing greenhouse gas emissions for our grandchildren, although there are immediate co-benefits if we do it right. It also means that we must adapt to a changing climate while we reduce emissions.
Statements by other scientific organizations are also important. The Joint Science Academies statement, signed by the Presidents of the academies of science of all G8 countries, as well as by those of China, India and Brazil, stated "climate change is real."
The IPCC and academies make scientific assessments but do not "do" science; they must build upon scientific research that is ongoing and supported by governments. And the science over the past five years has contributed new findings and concerns.
The climate system varies naturally (such as El Nino) and responds to natural external factors (solar variations, volcanoes, etc.), as well as human factors (greenhouse gases, aerosol pollutants, deforestation). If only natural factors were important, then scientists conclude that the climate would be cooling over the past 50 years, while it is observed to be warmed about 0.5 degrees. Only when the human factors are included can this warming be explained. A review of new science, published in May, 2005, states: "The recent research supports and strengthens the IPCC Third Assessment Report conclusion that "most of the global warming over the past 50 years is likely due to the increase in greenhouse gases." The climate of the future will be different than the climate of the past.
UNFCCC's objective is to achieve: "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system." New science is showing that "dangerous" may be reached for a global mean temperature change of about 2 degrees C, beyond pre-industrial levels, or about 1.5 degrees more. In addition, the climate system seems to be more sensitive to added greenhouse gases than previously thought so that a 2 degrees temperature change will be reached at lower levels of greenhouse gas concentrations.
New scientific results are also raising concerns about "irreversibilities" and "tipping points". For example, recent studies suggest that a further warming of between 1 and 2 degrees could result in the irreversible melting of the Greenland ice sheet with a resulting global sea level rise of 7 metres over a few thousand years. Warming may also upset the natural carbon cycle with resulting emissions from natural stocks in permafrost and under the oceans. There are also increased possibilities of turning off the major overturning circulation of the North Atlantic Ocean.
The IPCC in 2001 had projected likely future increases in the wind and precipitation intensities of hurricanes as the climate warms but had not been able to conclude anything about present trends.
With Katrina, Rita and Wilma very much in people's minds, new science has shown that although the number of hurricanes has remained about constant, the number of Category 4 and 5 hurricanes worldwide has nearly doubled in the last 35 years and the increase is consistent with the observed warming of the sea surface temperatures.
The Joint Science Academies statement said that actions must be taken to "reduce the causes [and] prepare for the consequences of climate change". How much action? How much change? To answer these questions requires continued investments in research and monitoring of the coupled atmosphere-ocean-land climate system.
Gordon McBean is a professor in the departments of Geography and Political Science and co-director of the University of Western Ontario's Institute for Catastrophic Loss Reduction. He was lead author of the IPCC in 1990 and 1995. This article was originally published in the Ottawa publication, Embassy.
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