Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 9:14 PM GMT on April 06, 2007
Significant climate change is already occurring, will grow dramatically, and will cause serious disruptions to natural ecosystems and the lives of billions of people world-wide over the coming century. We need to better prepare for the inevitable changes--and attempt to lessen the magnitude of the these changes by reducing greenhouse gas emissions as soon as possible. That's the take-home message from today's latest report from the United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC). Every six years, the IPCC releases a huge, influential study detailing the state of Earth's climate. Part 1 of the 2007 report, summarizing the science of climate change, was released in February. Today's summary, titled "Climate Change Impacts, Adaptation, and Vulnerability" addressed the likely impacts of climate change on Earth's ecosystems and people. Not all of the expected changes will be harmful--the IPCC emphasizes that "impacts of future climate change will be mixed across regions" for temperature rises of 1 to 3 �C above 1990 levels, with the big losers being the poor developing countries. However, if global warming exceeds 2 to 3 �C, the IPCC states it is very likely that all regions of the globe will suffer increased costs or declining benefits. I believe it is the responsibility of every citizen of the planet to take the 30 minutes needed to read the IPCC summary and familiarize themselves with what the world's top scientists say about the likely impacts of climate change. The scope and severity of the Earth-shaking changes that lie ahead present a breathtakingly formidable challenge for humanity.
Figure 1. Locations of significant changes in physical systems (snow, ice and frozen ground, hydrology, coastal processes) and biological systems (land, ocean, and freshwater) from 1970 to 2004. Between 90% and 100% of these changes are consistent with warming global temperatures, due in large part to human-emitted greenhouse gases. White areas are where not enough data existed to determine a temperature change. Figure 1 is a simplified form of Figure SPM-1 of the 2007 IPCC document, "Climate Change Impacts, Adaptation, and Vulnerability--Summary for Policy Makers."
Observed impacts of climate change to date
The IPCC report begins by summarizing observed changes in physical systems (snow, ice and frozen ground, hydrology, coastal processes) and biological systems (land, ocean, and freshwater) reported in 577 papers in the scientific literature between 1990 and 2004 (Figure 1). They conclude, "Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases." Examples for which they are highly (80% chance) or very highly confident (>90% chance) of include:
Earlier bird migrations and leaf unfolding
Poleward shifts in the ranges of various plant and animal species
Shifts in the ranges and numbers of ocean species near the poles
Earlier migrations of fish in rivers
Earlier and increased peaks in spring run-off from glacier- and snow-fed rivers
Warming of lakes and rivers
More and bigger glacial lakes
Medium confidence effects (50% chance of being true) observed in the Northern Hemisphere include:
Earlier spring planting of crops
Increases in forest fires and pest damage to forests
Heat-related deaths in Europe, spread of disease in some areas, and changes in allergenic pollen
Hunting and travel by humans over Arctic snow and ice
This is where the IPCC report gets very sobering. Keep in mind that the predicted future impacts may be understated, given the cautious nature of scientists--and the fact that the final version was edited by government officials, who changed the original conclusions of the scientists. I'll present just of few of the more mind-boggling impacts (in blue, with my comments in black), and leave the rest for the interested reader to discover:
The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification), and other global change drivers (e.g., land use change, pollution, over-exploitation of resources) (high confidence).
In other words, some ecosystems will collapse, putting the people who depend on these ecosystems in grave peril.
Many millions more people are projected to be flooded every year due to sea-level rise by the 2080s. Those densely-populated and low-lying areas where adaptive capacity is relatively low, and which already face other challenges such as tropical storms or local coastal subsidence, are especially at risk. The numbers affected will be largest in the mega-deltas of Asia and Africa while small islands are especially vulnerable (very high confidence).
Expect damage and human suffering from hurricanes to greatly increase in coming decades, thanks to higher seas levels.
There is medium confidence that at least partial deglaciation of the Greenland ice sheet, and possibly the West Antarctic ice sheet, would occur over a period of time ranging from centuries to millennia for a global average temperature increase of 1-4 �C (relative to 1990-2000), causing a contribution to sea level rise of 4-6 m or more.
Along with drought and ecosystem collapse, sea level rise is my big concern. Sea level before the most recent ice age was about 4-6 meters (13-20 feet) higher than today, at global temperatures that we expect to match by 2100. The IPCC states that a sea level rise of 0.6-1.9 feet (0.18-0.58 meters) is expected by 2100, and a 4-6 meter rise is not likely for centuries. However, our understanding of the response of glaciers to climate warming is poor. An unexpected rapid partial disintegration of the Greenland or West Antarctic ice sheets later this century raising sea levels by 2 meters (6 feet) has at least a 1% chance of occurring, in my opinion.
The language of the 2007 IPCC climate report is couched in uncertainly, but the broad picture is clear: future climate change may rival or exceed a World War in its effect on society. Steps to lessen its impact and adapt to it need to be made as soon as possible. The cost in lives, dollars, and human suffering will be far greater if we do not.
In his 2006 book, The Revenge of Gaia, philosopher-scientist James Lovelock writes, "I am old enough to notice a remarkable similarity between attitudes over sixty years ago towards the threat of war and those now towards the threat of global heating. Most of us think that something unpleasant may soon happen, but we are as confused as we were in 1938 over what form it will take and what to do about it. Our response so far is just like that before the Second World War, and attempt to appease. The Kyoto agreement was uncannily like that of Munich, with politicians out to show they do respond but in reality playing for time...Battle will soon be joined, and what we face now is far more deadly than any blitzkrieg."
The climate change storm is coming, and the wind is already starting to rise.
My next blog will be Monday afternoon or Tuesday. I've got several topics in mind--tornadoes in Chicago, Greenland glaciers, or hurricane model improvements.
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