The Baltimore Sun carries this article today on the predicted effects of climate change on Maryland. The article describes a report by a group of scientists who have compiled the first comprehensive report on the potential effects of climate change on Maryland. The report was prepared for the state by a committee of 19 scientists from five Maryland campuses, the U.S. Geological Survey and two environmental groups. Among the findings:
Coincidentally, another article on climate change was published in the Washington Post today. The article addresses the tendency of many to blame every hurricane, drought, heat wave, flood, frost or large cloud on global warming. This, of course, just confuses the issue because weather is naturally variable. If you attribute strong hurricanes to global warming then, when a year comes along without any strong hurricanes, people will logically say that global warming doesn't exist! So let's look at some facts. This graph [prepared by the National Oceanographic and Atmospheric Administration] shows the difference between the global average surface temperature from 1880 to 2006 and the average temperature during the period.
Coincidentally, another article on climate change was published in the Washington Post today. The article addresses the tendency of many to blame every hurricane, drought, heat wave, flood, frost or large cloud on global warming. This, of course, just confuses the issue because weather is naturally variable. If you attribute strong hurricanes to global warming then, when a year comes along without any strong hurricanes, people will logically say that global warming doesn't exist!
So let's look at some facts. This graph [prepared by the National Oceanographic and Atmospheric Administration] shows the difference between the global average surface temperature from 1880 to 2006 and the average temperature during the period.
Note that the data displayed here have been quality controlled to remove the effects of urbanization at reporting stations in and around cities. The average surface temperature has increased by about one degree fahrenheit since 1970 and, according to the Intergovernmental Panel on Climate Change, is now increasing by about 3.2 degrees fahrenheit each century.
Carbon dioxide concentrations in the atmosphere have increased from approximately 280 parts per million (ppm) in pre-industrial times to 382 ppm in 2006 - approximately a 36% increase according to NOAA's Earth Systems Research Laboratory. They also publish this nice graph.
Atmospheric carbon dioxide continues to increase at a rate of about 1.9 ppm per year. According to the IPCC's 2007 report, all of this increase is due to human activity.
Methane is more abundant in the atmosphere now than at any time in the last 650,000 years according to the IPCC report and are now 148% above pre-industrial levels.
Nitrous oxide levels have increased approximately 18% in the past 200 years and continue to increase. Increases in nitrous oxide are primarily due to agricultural activity and the use of artificial fertilizers.
These gases contribute to the increase in the temperature of the earth's surface and lower atmosphere through a process called the 'greenhouse effect', which was first described by Joseph Fourier in 1824. Without the greehouse effect, the earth would be a cold and barren planet unable to support life. But there can be too much of a good thing. The increase in atmospheric carbon dioxide, methane and nitrous oxide have increased the greenhouse effect and caused the average surface temperature to begin rising. Water vapor is also a major contributor to the greenhouse effect.
There are a variety of feedback mechanisms which have either a positive or negative effect on the increase in global temperature. Increased evaporation due to higher temperatures increase water vapor in the air which increases the greenhouse effect. On the other hand, clouds reflect solar energy back into space thus reducing the heating of the earth. It's uncertain how much the increase in water vapor will effect cloud formation. Reduced amounts of ice and snow increase absorption of solar energy by the earth's surface contributing to the increase in temperature.
One of the most pernicious effects of global warming is the increase in the mean sea level. Water, like most substances, expands slightly as it becomes warmer. In Maryland, and particularly on the Eastern Shore, this effect is increased by the slow subsidence of the land over a period of thousands of years. Here is a graph of sea level changes at Baltimore. It is prepared by the Permanent Service for Mean Sea Level (PSML) at the Proudman Oceanographic Laboratory.
While there are significant year-to-year variations, the trend is unmistakable. Much of Maryland, and particularly the Eastern Shore, is at a very low elevation and is very susceptible to inundation during periods of high tides and during storms. The photo above shows storm surge flooding caused by Hurricane Isabel in Bowleys Quarters, MD in September of 2003. With continued increases in sea level we can expect many more episodes like that. Many of the islands that existed in the Chesapeake Bay at the time of the explorations by Captain John Smith are now gone, victims of rising sea levels. We can expect more of the same.
For barrier islands like Assateague and Ocean City, the prognosis is also grim. The combination of rising sea levels and stronger storms made possible by increased ocean temperatures will make it increasingly difficult to maintain these islands in their current locations. This photo of barrier islands in North Carolina breached by Hurricane Isabel is a good example of what to expect.
(photo by the US Geological Survey)
So what can we do? I'll talk about that in my next post.