Weather and climate extremes have been affecting people around the world, from recent droughts in China and Australia to strong storms in Asia to a cold wave in large parts of Europe and the United States — all within a month of the World Meteorological Organization reporting 2008 would likely rank among the 10 warmest years on record. The cold wave sparked significant discussion, and the year 2008 ended up slightly colder than the previous year, partially because of the La Ni±a phenomenon. How could we speak of global warming in the middle of a cold wave in parts of the world? If 2008 was indeed cooler than 2007, is climate change real?
For scientists the answer is clear enough, as the examples mentioned are the result of natural climate variability, which does not contradict the human-induced long-term warming trend. This trend is reported in the Fourth Assessment Report of the United Nations WMO and Environment Programme cosponsored Intergovernmental Panel on Climate Change, which shared the 2007 Nobel Peace Prize.
Natural variability of the climate system is the cumulative result of four factors: first, the chaotic nature of the climate system; second, the oscillating behavior exhibited by a number of important processes, such as the El Ni±o–Southern Oscillation; third, variability in solar intensity, mainly determined by shifts in the Earth’s orbit and tilt and, to a much lesser degree, by variations in solar activity; and last, the random effect of volcanic eruptions forceful enough to inject sulfur dioxide and particulate material into the high atmosphere.
However, over the past 150 years, human activities have been increasingly changing the climate and producing a net warming. In particular, these activities have altered the natural greenhouse effect through an increase in carbon dioxide and other greenhouse gas levels because of deforestation and by emissions from fossil fuel combustion and land and animal use. The IPCC projects an increase in the occurrence and intensity of a number of weather and climate extremes as a result of climate change. Many of these events have likely changed in scope over the past 50 years, including increased occurrence of heat waves and heavy precipitation. At the same time, climate change is warming the planet, causing ice and snow to melt and sea level to rise.
The challenges posed by climate variability and change affect nearly every sector of society, including agriculture and fishery, water resources management, health, forestry, transportation, tourism and energy. These sectors are already experiencing increased risks in some regions and, although in some cases new opportunities may arise locally (wine grapes growing farther north, new transportation routes), long-term effects will overall be negative. Adaptation of these sectors will require local-scale climate predictions, tailored to a sector’s individual needs. At the same time, on the societal side, better interaction between climate information providers and users will be necessary.
Until now, climatologists had focused essentially on the larger picture and global trends; however, the present situation demands more efforts. To that end, WMO is working on a global framework for developing and providing climate services to meet users’ needs. In collaboration with its partners, WMO intends to launch such a framework at this year’s World Climate Conference-3 (August 31–September 4 in Geneva).
Scientists from many disciplines and decisions makers from governments, international and nongovernmental organizations, and the private sector will develop an agreement on actions needed to raise current scientific knowledge to the next level — by applying our knowledge to adaptation measures at increasingly local scales.
Take for example the food sector. The 2007 IPCC Fourth Assessment Report outlines the overall projections for Africa: By 2020, the report says, between 75 million and 250 million people are projected to be exposed to increased water stress due to climate change, while in some countries yields from rain-fed agriculture could be reduced by up to 50 percent, compromising basic access to food. A key objective is to downscale climate models to advise a farmer in the Sahelian region, for example, when the rainy season will start and how it will compare with previous seasons, for him to adjust and time his crops appropriately. WMO’s Regional Climate Forums are already helping to deliver such information to African farmers and others several months in advance.
The next step will be to enhance these services by fully integrating them into the decision-making process, which will require cooperation among all countries and many international partners. It is a necessary and highly cost-effective investment to ensure that we leave a sustainable situation to future generations.
Michel Jarraud is secretary-general of the U.N. World Meteorological Organization in Geneva.
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