Monday, July 09, 2012

U.S. experiences warmest 12-month period on record--again

And we are in a part of the climate cycle which is usually cooler than average. Note that when temps are compared to the "average", that the average has been increasing, so the difference is larger than it might appear.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2149

Posted by: Dr. Jeff Masters, 9:04 PM GMT on July 09, 2012

Thanks in part to the historic heat wave that demolished thousands of high temperature records at the end of June, temperatures in the contiguous U.S. were the warmest on record over the past twelve months and for the year-to-date period of January - June, said NOAA's National Climatic Data Center (NCDC) on Monday. June 2012 was the 14th warmest June on record, so was not as extreme overall as March 2012 (first warmest March on record), April (third warmest April), or May (second warmest May.) However, temperatures were warm enough in June to set a new U.S. record for hottest 12-month period for the third straight month, narrowly eclipsing the record set just the previous month. The past thirteen months have featured America's 2nd warmest summer (in 2011), 4th warmest winter, and warmest spring on record. Twenty-six states were record warm for the 12-month period, and an additional sixteen states were top-ten warm. The year-to-date period of January - June was the warmest on record by an unusually large margin--1.2°F.

Each of the 13 months from June 2011 through June 2012 ranked among the warmest third of their historical distribution for the first time in the 1895 - present record. According to NCDC, the odds of this occurring randomly during any particular month are 1 in 1,594,323. Thus, we should only see one more 13-month period so warm between now and 124,652 AD--assuming the climate is staying the same as it did during the past 118 years. These are ridiculously long odds, and it is highly unlikely that the extremity of the heat during the past 13 months could have occurred without a warming climate. Some critics have claimed that recent record warm temperatures measured in the U.S. are due to poor siting of a number of measurement stations. Even if true (and the best science we have says that these stations were actually reporting temperatures that were too cool), there is no way that measurement errors can account for the huge margin by which U.S. temperature records have been crushed during the past 12-month and 6-month periods.

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http://usnews.msnbc.msn.com/_news/2012/07/09/12643016-feeling-the-heat-first-half-of-2012-is-warmest-on-record?lite

By Vignesh Ramachandran, msnbc.com July 9, 2012

It's been a hot year.

In fact, the first six months of 2012 accounted for the warmest January-through-June period on record for the contiguous U.S., the National Oceanic and Atmospheric Administration (NOAA) announced Monday.

The national temperatures averaged 52.9 degrees — "4.5 degrees above the long-term average," NOAA said in a statement. "Most of the contiguous U.S. was record and near-record warm for the six-month period, except the Pacific Northwest." East of the Rockies, 28 states were "record warm," NOAA said.

The past year also registered as the hottest 12-month period on record in the contiguous U.S., narrowly surpassing the mark set last month, NOAA said.

6 comments:

rjs said...

the 1 in 1,594,323 odds are a bit of nonsense, really…temperatures tend towards the trend…a 90F day is more likely to follow a 90F day than a 70F day...& warm dry winters with little snowpack beget hot dry summers…

Patricia said...

But the temps have been getting trending upward. And we are in a part of the weather cycle when it would normally be getting cooler.

rjs said...

i understand all that, patricia...my argument is with computing odds on physical phenomena with exogenous influences...the point is just that warmer than normal weather tends to persist, but the odds were computed as if each month were an independent "coin flip" with no extenuating circumstances...

Patricia said...

Thanks, rjs. Sorry it took so long to publish your comment. I've been quite busy lately.
I just did a quick calculation, and it looks like you're right about how they calculated it.
It seems to me that the normal pattern of such things would affect whether this is a reasonable probablility. Like, if an above average warm period rarely lasted more than three months, the marginal probabilities for the following months might not be that high?

rjs said...

in my first comment i mentioned the lack of a snowpack; just a dearth of upper plains snow changes the odds...a lack of winter snowpack reduces albedo and allows the ground to heat up faster in the spring...also, the resulting lack of ground moisture contributes to hotter & drier summers...so a warm winter with little snow is a good forecaster of a hot summer...

Patricia said...

Well, I don't see how we can calculate the exact probabilities, with so many variables.
All we can do is get a reasonable approximation.
I don't particularly care about the exact probabilities. We have a big problem and we need to focus our energies on minimizing the damage.

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