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U.S. Experiences Warmest 12-Month Period On Record And Most Extreme January to April

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"U.S. Experiences Warmest 12-Month Period On Record And Most Extreme January to April"

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Figure 1. The ten warmest 12-month periods in the contiguous U.S. since record keeping began in 1895. Image credit: NOAA/NCDC.

by Jeff Masters, via WunderBlog

The past twelve months were the warmest twelve months in U.S. history, said NOAA’s National Climatic Data Center (NCDC) on Tuesday, in their monthly “State of the Climate” report. Temperatures in the contiguous U.S. during May 2011 – April 2012 broke the previous record for warmest 12-month period, set November 1999 – October 2000, by 0.1°F. The past twelve months have featured America’s 2nd warmest summer, 4th warmest winter, and warmest March on record. Twenty-two states were record warm for the 12-month period, and an additional nineteen states were top ten warm. NOAA said that the January – April 2012 period was also the warmest January – April period since record keeping began in 1895. The average temperature of 45.4°F during January – April 2012 was 5.4°F above the 20th century average for the period, and smashed the previous record set in 2006 by an unusually large margin–1.6°F.


Figure 2. The average temperature of 45.4°F during January – April 2012 was the warmest on record: 5.4°F above the 20th century average for the period, and was 1.6°F above the previous record set in 2006. January – April temperatures have been rising at about 1.9°F per century since 1895. Image credit: NOAA/NCDC.

April 2012: 3rd warmest on record
April 2012 was the third warmest April in the contiguous U.S. since record keeping began in 1895. Ten states had a top-ten warmest April, and no states were cooler than average. But what’s really remarkable about April was that eight states–Illinois, Indiana, Kentucky, Michigan, Wisconsin, Ohio, Pennsylvania, and West Virginia–had average April temperatures cooler than their March temperatures, even though their April temperatures were still above the long-term average for the month. These statistics show just how remarkably warm March 2012 was. Most extreme was Illinois, where April 2012 temperatures ranked in the top 20% for warmest Aprils, yet were cooler than March 2012 temperatures.


Figure 3. Temperature rankings for April 2012 in the Contiguous U.S. Ten states had a top-ten warmest April, and no states were cooler than average. Image credit: NOAA/NCDC.


Figure 4. NOAA’s U.S. Climate Extremes Index (CEI) for January – April shows that 2012 had the most extreme weather on record.

Most extreme January – April on record
NOAA’s U.S. Climate Extremes Index (CEI), an index that tracks the highest 10 percent and lowest 10 percent of extremes in temperature, precipitation, and drought, was 42% during the January-April period, over twice the average value, and the greatest on record. Remarkably, 82% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically, and 68% had warm minimum temperatures in the top 10%, with records going back to 1910. The previous records were 56% (2000) and 57% (1992) for maximum and minimum temperatures, respectively. The percentage area of the U.S. experiencing top-10% drought conditions during January – April was 19%, which was the 17th greatest since 1910. Extremes in precipitation as computed by the CEI were near average for the January – April period.

– Jeff Masters co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990. This piece was originally published at the WunderBlog and was reprinted with permission.

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5 Responses to U.S. Experiences Warmest 12-Month Period On Record And Most Extreme January to April

  1. Barry Saxifrage says:

    As Hansen says 350ppm is the safe level…and we are at 396ppm now.

    Already extreme heat events have gone from 0.2% of the earth surface to 10% in the last 50 years. And we haven’t even had 1C warming yet.

    The weirding is just getting started. It just gets worse from here on out.

    • wili says:

      I’m not sure Hansen ever said that 350 was “safe”–just that this is the point at which we can be quite sure that bad and unreversible (like the melting of the icecaps) developments start occuring.

      Since CO2 levels had been below 300 for thousands of years (at least) before the industrial age, this is the number below which we could be reasonably assured of a safe and stable climate.

  2. Kathleen sea says:

    And Americans just keep buying huge SUVs, failing to recycle or heat/ cool their homes responsibly, etc. selfish mentality has created this condition, and the whole world reaps the result

  3. Jeff in Iowa says:

    Here in Iowa, for generations, gardeners were told to wait until Mother’s Day to plant sensitive garden vegetables (such as tomatoes) so as to avoid the last freeze.

    In the late 90s, I began noticing that the actual weather was no longer playing by that old rule. So I started planting my tomato plants in late April. And I’ve been doing so every year since, with no problems.

    My folks visited in late April and they became aware that I was getting ready to plant my tomatoes the next day. They expressed concern — “what are you thinking” they asked.

    I told them I’ve been doing this for more than 10 years and it’s worked fine. “The climate is changing Mom and Dad,” I explained.

    You should have seen the looks on their faces! All they ever watch is Fox News. It was as if it had never before occurred to them that the climate is, in fact, changing.

  4. squidboy6 says:

    I just traveled across the Deep South through Texas, New Mexico, and Arizona finally ending up in Pasadena. It’s a miserable drive… but in the middle of Texas I noticed a stand of two hundred year old oaks near the road and most of them were dead. A few had some buds and leaves on the northern side of the trees.

    These were not old diseased oaks. They were in the prime of their growth and they were probably killed by the drought last year. Nearby oaks, ones near dwellings, were alive and the same size and shape, full branches with little dead wood. The nearby oaks were alive, probably because the homes they were near had septic systems and the water was available from there.

    This Summer should be a really bad one there. It looks like drought again. What will it take to get some of these people to have doubts about the corporate news-media? I think I’ll take a Northern route back. It was 114 degrees last time I went through Phoenix in the Summer and not much cooler in Texas. Sure were a lot of “lone stars” on the bridges, buildings, and signs there!