Federal Advisory Committee Draft Climate Assessment Report
By Paul Homewood
The US government, or more specifically their National Climate Assessment and Development Advisory Committee, have just released their draft climate report, which states that “Climate change is already affecting the American people”.
One claim made is that “certain types of weather events have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts.”
This is all very strange, because the US Geological Service issued their own report in 2011, saying the exact opposite. According to them:-
Only one of four large regions of the United States showed a significant relationship between carbon dioxide (CO2) in the atmosphere and the size of floods over the last 100 years. This was in the southwestern region, where floods have become smaller as CO2 has increased.
A new report published by U.S. Geological Survey scientists in the Hydrologic Sciences Journal looks at this potential linkage using historical records of floods throughout the nation. Scientists studied flood conditions at 200 locations across the United States looking back 127 years through 2008.
"Currently we do not see a clear pattern that enables us to understand how climate change will alter flood conditions in the future, but the USGS will continue to collect new data over time and conduct new analyses as conditions change," said USGS scientist and lead author Robert Hirsch. "Changes in snow packs, frozen ground, soil moisture and storm tracks are all mechanisms that could be altered by greenhouse gas concentrations and possibly change flood behavior. As we continue research, we will consider these and other factors in our analyses."
The decrease of floods in the southwestern region is consistent with other research findings that this region has been getting drier and experienced less precipitation as a likely result of climate change.
Climate changes that could influence flood magnitudes include shifts in the intensity and tracks of various types of storms and changes in the type of precipitation (rain versus snow). The conditions on the landscape when large storms arrive can also change (for example, smaller snowpacks, less soil moisture and less frozen soil). All of these can influence the size of floods. Of course, human activities within the watershed can also have a major influence in the size of floods. These include urbanization, building of dams and levees, and shifts in vegetation types and drainage of soils and wetlands. At the present time, we see much larger changes in flooding from these causes than we can see from greenhouse forcing.
The draft report contains many more such alarmist claims, but if it so inaccurate regarding floods, is it worth the paper it is written on?