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Scientists Say Climate Change is Contributing to More Extreme Weather Now

Steve Fleischli

Posted September 7, 2011

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Recently, NRDC published a report explaining the potential water-related impacts of climate change on U.S. cities.  The projected impacts include, among other things, more frequent and intense storm events.  Now, some scientists say the effects of climate change are already contributing to more extreme weather events in the U.S. and elsewhere.  Climate scientists from NCAR, Scripps and Weather Underground discussed their findings on a conference call today.  Most of what was covered in the call can be found on the Climate Communication website.

As we have all seen, extreme weather events, such as blizzards, tornadoes, flooding, droughts, heat waves, and tropical storms, have occurred within the past few years both in the U.S. and across the globe.  Scientists say record-breaking extremes are occurring as heat-trapping gases allow the atmosphere to warm and hold more moisture, which provides fuel to these events.  They say the relatively small observed increase in average temperature over the 20th century (about 1°C) is causing large changes in extreme events. 

Because human activity has changed the background environment in which weather events develop, they have concluded that climate change is now a component of all weather events—on the scale of 5 to 10 percent.  For example, analysis indicates that precipitation from Hurricane Katrina in 2005 was greater by 6 to 8 percent due to climate change, which may not seem that much but is equivalent to an additional inch of rain on top of a foot.

Climate change is compounding natural variability to cause record-breaking extreme weather events.  One scientist on today’s call equated greenhouse gases to steroids in the climate system—effectively loading the dice or shifting the odds in favor of more climate extremes. 

Data also show that record high temperatures now outpace record lows. Historically, the ratio of record daily temperature highs to record daily lows has been roughly 1 to 1.  However, in the past decade, this ratio has increased to 2 to 1—the amount of record daily highs being set each year is now twice that of daily lows.  So far in 2011, this ratio is 3 to 1.  Climate models project that this ratio will further increase to 20 to 1 by mid-century and 50 to 1 by 2100 at the rate of current emissions.  Further warming due to greenhouse gases also will lead to additional warming of the oceans and more moisture in the atmosphere and manifest itself in the form of more intense, larger, and longer-lasting storms. 

The linkage between climate change and tornadoes is more complex because of the many factors involved (e.g., high altitude wind patterns, topography, etc.) but the scientists say climate change is leading to more moisture and warm air from the Gulf of Mexico and tropical Atlantic, which fuels the formation of supercell thunderstorms. 

Finally, the observed warming cannot be explained by phenomena other than increased concentrations of greenhouse gases, as there have been no changes in solar activity or clouds that would sufficiently explain observed temperature increases.

The types of extreme weather we have seen this year are certainly consistent with what models project in a changing climate.  Today’s announcement makes a more direct connection and reinforces the notion that how we have treated and continue to treat the planet may be increasingly reflected in how it treats us.

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rfSep 8 2011 12:29 AM

Uhh... do these "climatologists" ever talk to solar scientists? No significant increase in solar activity to explain these shifting weather patterns? REALLY?! Considering it's September 7th, and we've had 2 X class flares in the past 36 hours! And 4 prior major CME events this year alone. Starting Feb. 15th with an X2. The KP index has been relatively unstable this year, with being as high as a KP=7. Ice caps melting on Mars. I suppose that has to do with our Carbon emissions too. People we are in an increased period of solar activity, and our solar system is showing us the evidence. Don't buy into this man made climate change nonsense.

mdSep 8 2011 11:49 AM

Of course they do...they will continue to change their story to match the circumstances. It is a very convenient and unmeasurable phenomenon. The length of time we have been observing and recording global climate - does not constitute a valid sample size for Earth's climate over the many millenniums of history.

Mind you - being anti-global warming does NOT make me anti-enviroment. It's just that there is equal data to refute global warming as there is to support it.

Dana PearsonSep 9 2011 01:03 AM

you paid corporate shills will someday be tracked down and made to pay for your sellout of our children. I don't know how you can look yourselves in the mirror. Disgusting ignorant traitors to the human race.

It would be one thing if there weren't an abundance of clean, safe solar options staring us in the face. However, we do have many choices and the only thing holding us back is the entrenched vested interests who are spending their ill gotten goods to support denialist trolls like you fools selling your souls and betraying all of the innocents who will someday spit on your graves.

Alastair IrvineSep 9 2011 11:46 AM

I agree that scientists should talk "between disciplines". However, the 100-year consistent rise of atmospheric carbon dioxide isn't going away. Compared to this, solar activity variation is minor. And don't forget, they even proved on Mythbusters that the greenhouse effect is real.

97% of climate scientists can't be wrong. Human-caused climate change is real, as much as I don't want it to be.

Tom GraySep 9 2011 05:08 PM

Interesting, both of the denier comments are made by folks with two-initial handles. I wonder whether they are indeed distinct individuals.

rfSep 9 2011 10:18 PM

Dana- Nice emotional comment... And I can tell your "loving nature" by how you so intimately express yourself. Truly a wonder of the human race. You care for "our" children, yet care nothing for those around you. Your humanist ideology is sickening, and is the true thing killing the human race.

Alastair- Since when is "Mythbusters" a credible scientific source? You treat them as though their Caltech or MIT. It's a TV show! For entertainment!

Tom- The persistent internet skeptic, healthy attitude. I assure you however neither am I md, nor am I some "government" disinformation agent.

Tony KerrSep 11 2011 07:18 AM

The comments by deniers are similar to those that hounded Galileo many years ago. Then, as now, science is positing facts that cause discomfit to power structures (whether religious or corporate)..

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