Global temperature in 2003 was the hottest in the historical record, and the temperature increase over the 20th century is likely to be the highest of the past millennium. Global average temperatures have warmed about one degree Fahrenheit (0.6C) since 1900. The ten warmest years on record have occurred since 1987, seven of them since 1994.
This article highlights early and emerging warning signs of global warming for each of the world's regions, namely, Africa, Antartica, Asia, Central America, Europe & Russia, North America, Oceania, and South America.
The African continent is a rich mosaic of ecosystems, ranging from the snow and ice fields of Kilimanjaro to tropical rainforests to the Saharan desert. Although it has the lowest per capita fossil energy use of any major world region, Africa may be the most vulnerable continent to climate change because widespread poverty limits countries' capabilities to adapt. Signs of a changing climate in Africa have already emerged: spreading disease and melting glaciers in the mountains, warming temperatures in drought-prone areas, and sea-level rise and coral bleaching along the coastlines.
The impacts of warming temperatures in Antarctica are likely to occur first in the northern sections of the continent, where summer temperatures approach the melting point of water, 32F (0C). Some ice shelves in the northernmost part of Antarctica - the Antarctic Peninsula - have been collapsing in recent years, consistent with the rapid warming trend there since 1945. Scientists are also concerned about future changes in the large West Antarctic ice sheet on the main continent because its collapse could raise sea level by as much as 19 feet (5.8 meters).
The Asian region spans polar, temperate, and tropical climates and is home to over 3 billion people. As the climate warms, many mountain glaciers may disappear, permafrost will thaw, and the northern forests are likely to shift further north. Rapid population growth and development in countries like China and India will put additional pressures on natural ecosystems and will lead to a rapid rise in the release of greenhouse gases into the atmosphere unless steps are taken to curtail emissions.
The climate of Central America strongly affects social and economic conditions in the region through its impacts on agriculture, tourism, and human health. The impacts of the 1997-98 El Nino in Central America provide examples of what future climate warming may bring. During that year, forest fires raged out of control and high sea surface temperatures "bleached" corals in adjacent seas. Future changes in the frequency of extreme events such as hurricanes, floods, and droughts may damage important export crops such as bananas, threaten human settlements on unstable hillsides, and facilitate the outbreak of diseases such as malaria and dengue fever.
Europe's natural ecosystems are generally fragmented and disturbed, making them very sensitive to climate change. Most of Europe experienced temperature increases over the past 100 years that are larger than the global average, and precipitation generally increased in the north but decreased in the south. The warming is clearly noticeable in mountain regions by the widespread retreat of glaciers in the Alps.
Plant and animal species are also apparently responding to the changes by shifting their ranges northward and by changing the timing of their activities to coincide with an earlier spring. The fragmented nature of the European landscape, however, may make it difficult for less adaptive species to respond to continued climatic warming.
For Europe (and North America) we have many more hotspots than for some other regions of the world, although impact studies have been emerging in larger numbers in recent years from previously under-studied regions. This higher density of early warning signs in Europe is due in part to the fact that these regions have more readily accessible climatic data and more comprehensive programs to monitor and study environmental change, in part to the disproportionate warming that has been observed over the mid-to-high-latitude continents compared to other regions during the last century, and in part to emphasize the importance of the industrialized countries of Europe taking strong action to reduce greenhouse gas emissions.
The vast North American continent ranges from the lush sub-tropical climate of Florida to the frozen ice and tundra of the Arctic. Within these extremes are two wealthy industrialized countries with diverse ecosystems at risk. Yet the United States and Canada are two of the largest global emitters of the greenhouse gases that contribute to a warming climate. Examples of all 10 of the "hotspot" categories can be found in this region, including changes such as polar warming in Alaska, coral reef bleaching in Florida, animal range shifts in California, glaciers melting in Montana, and marsh loss in the Chesapeake Bay.
For North America we have many more hotspots than for some other regions of the world, although impact studies have been emerging in larger numbers in recent years from previously under-studied regions. This higher density of early warning signs in the US and Canada is due in part to the fact that these regions have more readily accessible climatic data and more comprehensive programs to monitor and study environmental change, in part to the disproportionate warming that has been observed over the mid-to-high-latitude continents compared to other regions during the last century, and in part to capture the attention of North Americans who need to take action now to reduce greenhouse gas emissions.
The Oceania region ranges from the lush tropical rainforests of Indonesia to the interior deserts of Australia. The climate is strongly influenced by the ocean and the El Nino phenomenon. Small island nations and the coastal regions - where much of the population is concentrated - are very vulnerable to increasing coastal flooding and erosion due to rising sea level. Warming sea temperatures in recent years have damaged many of the region's spectacular coral reefs, threatening one of the world's most diverse ecosystems.
The people of South America are heavily dependent on the continent's natural resources - from the rangelands at the foothills of the Andes, to the plants and animals of the Amazon rainforest, to the fisheries off the coast of Peru. The region's ecosystems are particularly vulnerable to the changes in water availability expected with a changing climate. Higher global temperatures along with more frequent El Ninos may bring increased drought, and melting glaciers in the Andes threaten the future water supply of mountain communities.
Signs of a warming climate have already appeared both at high elevations - in glacial retreat and shifting ranges of disease-carrying mosquitoes - and along the coast - in rising sea level and coral bleaching.
James Nash is a climate scientist with Greatest Planet (www.greatestplanet.org). Greatest Planet is a non-profit environmental organization specialising in carbon offset investments.
James Nash is solely responsible for the contents of this article.