A guest post by Mike Smith, CCM and AMS Fellow.
The Midwest floods were rolling downstream last week, setting river stage records in Iowa, bursting levees on the Mississippi, and causing thousands to be displayed from their homes. Billions have been lost in damaged and destroyed property and 24 lives lost.
In the midst of this tragedy, the National Climatic Data Center (NCDC) and the Environmental Defense Fund (EDF) tried to capitalize on heightened public interest with an attempt to gain headlines by tying these tragic events to “global warming.”
The EDF proclaimed: Did Humans Cause the Midwest Flooding? In the piece, EDF’s James Wang writes, “Another element [of the Midwest floods] may be global warming, which increases the probability of extreme weather events like torrential rain.” NCDC, a part of the National Oceanic and Atmospheric Administration, headlined, Extreme Weather to Become More Common. The respective headlines can be found at http://environmentaldefenseblogs.org/climate411/ and www.noaa.gov/ .
This is fear mongering, not the advancement of science. And, it detracts from NOAA as a whole because its National Weather Service performed heroically – with its field staff working long hours coping with the floods and accompanying tornadoes and severe thunderstorms.
It is unseemly to work to score public relations points when people are losing their homes, their crops, and their lives.
And, it leaves us to ponder a key question: Does the science justify tying the Midwest floods to Global Warming? My answer? An emphatic “no.”
In explaining its contention EDF says, “Global warming intensifies the ‘hydrological cycle’ – the process in which water evaporates into the air, forms clouds, and then rains back down on the Earth.” While that contention that global warming intensifies the hydrologic cycle is itself speculative (for reasons outside the scope of this posting), the fact is a given tornado or rainstorm responds to weather, not climate, conditions.
EDF author James Wang goes on to say, “Global warming doesn’t fully explain the catastrophe in the Midwest, but it likely [emphasis mine] plays a role.” The contention that “warming” is linked to catastrophic Midwest floods is relatively easy to test. Here’s how: What were the temperatures during this and similar floods in the region?
When the atmosphere creates weather it is responding to the conditions that exist in the lower atmosphere at the time of the event – temperatures, pressures, humidity, etc. From a weather perspective, what is the trend of global temperatures in the lower atmosphere when the intense rainstorms were created? Anthony Watts provides this graph of satellite-measured lower tropopsphere temperatures:
As these figures demonstrate, lower tropospheric temperatures (the part of the atmosphere where weather is generated) have reverted to the levels of 11 years ago after a period of rapid cooling over the last year and a half. In addition to RSS, the other three measures of world temperatures reveal the same cooling pattern: http://www.woodfortrees.org/plot/hadcrut3vgl/from:1997/to:2009/offset:-0.146/plot/gistemp/from:1997/to:2009/offset:-0.238/plot/uah/from:1997/to:2009/plot/rss/from:1997/to:2009 . As Dr. Roger Pielke Sr. has previously discussed, the oceans (the more important indicator of global temperature change) have not been warming in recent years and have actually cooled slightly. The “warming” conditions explict in the EDF claim and implicit in the NOAA release do not exist.
As a clue as to what temperature temperature pattern, if any, might really be associated this year’s floods, compare the temperature drop depicted on the RSS graph from January, 2007 to May, 2008 with the drop during months 150 to 170. This cooling is widely attributed to the June, 1991, (month 149 on the graph) eruption of Mt. Pinatubo. That explosive volcanic eruption spread particulates into the stratopshere, shading the earth and cooling the lower atmosphere. A period of extremely heavy rains began in the Plains and Midwest in months 169 and 170 (depending on location) that lasted well into summer resulting in the Great Flood of 1993 in many of the same areas that were in flood last week. In both cases, temperatures were far lower than in the peak year of 1998.
Why might Midwest flooding be linked to rapid cooling? Here is some “educated speculation”: Oceans lose heat more slowly than land. The Gulf of Mexico is the primary source of the low-level moisture that feeds weather and storms in the Midwest. A warm Gulf can provide large amounts of moisture. However, over North America, temperatures have been unusually cool (c.f., Anchorage sets record for latest ‘first 70° temperature’ of the year, story from June 20, 2008, http://wattsupwiththat.wordpress.com/2008/06/20/anchorage-sets-new-record-for-latest-high-temp-day/ ) and, from June 6, 2008 NCDC provides further evidence in its “U.S. Has 36th Coolest Spring on Record” (www.noaanews.noaa.gov/stories2008/20080606_ncdcspring.html ). The accompanying map reveals the Midwest was colder than normal. By contrast, the Gulf Coast states were considerably warmer. Texas was warmer than normal with “normal” temperatures in Louisiana, Mississippi and Alabama. These states’ temperatures were strongly influenced by the warm Gulf air flowing over on them its way north to the Midwest.
Basic meteorological principles indicate that persistent cold air to the west and north and warm, moist air to the south and east is a recipe for frequent intense thunderstorms. This pattern was certainly in evidence during spring 2008. The map accompanying NOAA press release shows this pattern in more detail: http://www.noaanews.noaa.gov/stories2008/images/03-05Statewidetrank_pg_final.gif . Higher numbers equal warmer temperatures. Note how it was warm in Louisiana (70th) and progressively cooler with each state to the north: Arkansas (31), Missouri (26), Iowa (24), and Minnesota (23). The Northwest was extremely cold with Oregon reporting the 15th coldest spring since records began. This is an ideal pattern for frequent thunderstorms with heavy rains.
If last week’s Iowa flooding and world temperatures are linked in the way the EDF contends (i.e., higher world temperatures result in more Iowa flooding), there would have been record flooding in Iowa in 1998. While June, 1998 was wet in southern and eastern Iowa (www.cpc.noaa.gov/products/analysis_monitoring/regional_monitoring/palmer/1998/06-20-1998.gif ) major flooding approaching the scale of 1993 or 2008 did not occur.
The record Midwest floods of 1993 and 2008 occurred after periods of rapid cooling. The warmest year, 1998, did not have Midwest floods anywhere near the magnitude of those in 1993 and 2008. It is my judgment the attempt to link the 2008 floods to Global “Warming” is completely unjustified.
Mike Smith is a certified consulting meteorologist and a Fellow of the American Meteorological Society and the opinions stated above represent his personal point-of-view. He is CEO of WeatherData Services, Inc., an AccuWeather Company, based in Wichita. AccuWeather’s global warming blog can be viewed at: http://global-warming.accuweather.com/ .