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The average global temperature for 2004 of 14.60 degrees Celsius (58.28 degrees Fahrenheit) makes it the fourth warmest year on record. October and November of 2004 were the hottest of those months on record since recordkeeping began in 1880. February of 2004 was the second warmest, and March, April and December were the third warmest of those three months.
(See data for figure.)
These record-breaking readings, which come from the global series maintained by NASA’s Goddard Institute for Space Studies, continue a trend of rising global temperatures. The average temperature of 14.01 degrees Celsius in the 1970s rose to 14.26 degrees in the 1980s. In the 1990s it reached 14.40 degrees. And during the first five years of this new decade, it has averaged 14.59 degrees Celsius.
In fact, the five hottest years on record have all occurred within the last seven years. Of these five, 1998 was the warmest year on record, with an average global temperature of 14.71 degrees Celsius.
Rising temperatures are due primarily to the buildup of carbon dioxide (CO2) in the atmosphere from the burning of increasing amounts of fossil fuels. Once released into the atmosphere, CO2 traps heat that would otherwise escape back into space. And emissions of CO2 have been rising since the start of the Industrial Revolution in 1760, causing temperatures to climb.
As carbon emissions continue to increase, so will the pace of climate change. During the past century, temperatures rose 0.6 degrees Celsius, with most of the increase occurring during the last three decades. But the average global temperature is projected to rise 1.4—5.8 degrees Celsius by 2100, according to the Intergovernmental Panel on Climate Change, a global body of more than 1,500 scientists. The increase is expected to occur unevenly, with higher elevations and higher latitudes experiencing greater temperature changes than lower elevations and equatorial regions.
There is little question that a global temperature increase in the upper range of predictions would be highly disruptive. A report prepared for the U.S. Department of Defense in 2003 investigated the security implications of abrupt climate change over the next 20 years. One scenario showed that rising temperatures could bring large-scale drought in critical agricultural regions worldwide, extreme temperature drops in some regions and searing heat in others, and civil unrest and mass migrations from spreading insecurity about water and food supplies.
Even at the lowest projected temperature increases, climate change models predict more frequent and more severe storms, floods, heat waves, and droughts—all of which affect ecological biodiversity, human health, and economic security. Indeed, although we have only experienced temperature increases of a half-degree Celsius over the past several decades, the effects of climate change can already be seen in different parts of the world.
In May 2003, for example, 1,600 people died in a record heat wave in India, where death tolls from heat in the thousands are no longer uncommon. Three months later, another 35,000 people died in Europe from a heat wave that lasted for weeks. The record-breaking temperatures damaged crops across the continent, contributing to a 13 percent drop in the European grain harvest that year.
In the United States, a recent report by the Pew Center on Global Climate Change analyzing the results of 40 previous studies found a clear link between increased temperatures and numerous changes in natural systems across the country. Warmer winters, increased precipitation, and earlier springs are causing certain plant species to bloom several weeks earlier, disrupting insect food supplies and plant pollination cycles. Some animals are responding to warmer temperatures with shortened hibernation cycles, sometimes up to 23 days earlier than just 15 years ago, putting them at risk for starvation as they wait for spring food to become available. Temperature changes have led to shifts in many species’ habitats as populations move north and to higher elevations in search of cooler temperatures; it is estimated that about half of all wild species in the United States have already been affected by climate change.
Similar effects of rising temperatures are being documented worldwide. Ice and snow cover have shrunk 30 percent in the Himalayas over the past 30 years, increasing risk of flooding and glacial lake overflow. In Europe, spring events such as flower blooms have occurred progressively earlier since the 1960s, while fall events such as leaf color changes have been delayed each decade. These seasonal shifts have introduced species to new areas and disrupted migratory patterns of birds.
A new study by 300 scientists and indigenous leaders from eight countries over four years concluded that the Arctic, where warming has occurred at nearly twice the global average rate, “is now experiencing some of the most rapid and severe climate change on earth.”
Siberia and Alaska have already warmed 2–3 degrees Celsius since the 1950s. Snow cover in the Arctic has shrunk by 10 percent, and summer sea ice cover is 15–20 percent smaller than it was 30 years ago. If these recent trends continue, polar bears are not likely to survive to the end of the century as melting ice shrinks their habitat and compromises their access to food. Tundra and permafrost are also thawing rapidly across the Arctic, threatening the survival of many land species and hampering transportation.
The increasing risks and costs related to these rapid temperature increases are already forcing Arctic coastal communities such as the Alaskan village of Shishmaref and industrial facilities such as the Pechora Sea oil storage facility to consider relocating. Not only do these changes affect the well-being of those in the Arctic, they also give an indication of the sort of change that lies ahead in the rest of the world as temperatures continue to rise during the twenty-first century.
This year’s temperature data provide further evidence of what some scientists are calling a new geological epoch, the Anthropocene, in which human activities are the main driver of the global climate system. The amount of temperature increase beyond the lower-end projections depends on what we do now to curb carbon emissions and other greenhouse gases. We can continue using climate-disrupting fossil fuels, or we can choose to shift to renewable energies, more-efficient technology, and proactive climate change policies.
Copyright © 2005 Earth Policy Institute