Rajendra K. Pachauri, a former assistant N.C. State University professor, is chairman of the United Nations' Intergovernmental Panel on Climate Change. The panel shared the 2007 Nobel Peace Prize with former Vice President Al Gore. The following remarks were included in a speech Monday at the Emerging Issues Forum.

The Intergovernmental Panel on Climate Change's Fourth Assessment Report, which was completed in 2007, highlights the fact that warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

Over the past 100 years, the world has experienced warming of about 0.74 degrees Celsius. These changes in temperature translate into many effects -- such as changes in precipitation, droughts, extreme events, sea level rise -- that adversely affect human and natural systems.

Continued greenhouse gas emissions at or above current rates would cause further warming, which would induce many changes in the global climate system that would very likely be larger than those observed during the 20th century. effects on poor regions: The number of people exposed to increased water stress [when demand exceeds the available water during a certain period or when poor quality restricts use] by 2020 is projected to include 120 million to 1.2 billion in Asia and 75 million to 250 million in Africa. If coupled with increased demand, this will adversely affect livelihoods and exacerbate water-related problems.

It is projected that agricultural yields could drop by up to 50 percent by 2020 in some African countries. In Africa, crop net revenues could fall by as much as 90 percent by 2100, with small-scale farmers being the most affected. This would further adversely affect food security and exacerbate malnutrition.

These consequences, associated with increased number of extreme events and sea level rise, could translate into large numbers of displaced people. The impact of climate change on the most vulnerable communities could threaten world security.

From local to global responses: Local authorities have the responsibility as well as the opportunity to lead the way toward a reduction in greenhouse gases contributing to climate change. Urban activities generate close to 80 percent of carbon dioxide as well as significant amounts of other greenhouse gases. One of the opportunities brought up by climate change is to work toward more sustainable cities and to improve the quality of life for residents.

In the U.S., action from the states is also important, as states have primary jurisdiction over many areas (electric generation, agriculture and land use) that are critical to addressing climate change. Many states have taken the lead on developing climate policies and initiatives.

Local, state and regional actions are vital to the change that is needed to halt the warming risk, but they cannot substitute for a coordinated national response. Early involvement in the growing global consensus for deep cuts in emissions would also ensure competitiveness of businesses in a world market dominated by low-carbon products.

International action on mitigation is currently driven by the Kyoto Protocol, which entered into force in 2005. The Kyoto Protocol is, however, constrained by modest emission limits and should be followed up by measures to achieve greater reductions.

Developed countries have a historical and moral responsibility to take the first steps toward a low-carbon society. In developing countries, emissions would need to drop below their projected baseline emissions within the next few decades. Taking a longer-term perspective, equitable targets should be defined in terms of per-capita greenhouse-gas emissions. At present, per-capita emissions range from less than one ton of carbon dioxide equivalent per year in the least developed countries to about 20 tons equivalent per year in some developed nations.

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