How to read the weather extremes in the era of climate change

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The ratio of hot and cold weather extremes in recent U.S. history.

February 25, 2013. In the past year, the weather in the United States has established several unpleasant records that auknulos billions of dollars in damage and aggravated endless arguments about how it's all linked to climate change. And, as is often the case, while scientists are trying to get to the truth, man in the street is "all clear."

To add to this public discussion a little bit of common sense at the annual conference of the American Association for the Advancement of Science held a seminar on the subject. The audience particularly memorable three performances: one concerned the state of the American climate in general, and the second was devoted to recent developments, the third — the way it all to convey to the public.

The first orated Donald Ueblz from the University of Illinois. He began by saying that the climate can be expressed as a Gaussian function: extreme heat and cold are deposited on the left and right of the "bell". From this perspective, climate change may manifest itself in three ways. The curve will shift, if the heat will become more frequent and cold — to become more rare. The curve flattened if the weather extremes will become more frequent. Finally, both may occur simultaneously.

And a lot depends on what aspect you are interested in climate.

When it comes to temperature, both the world and in the United States, the curve has shifted: heat comes more often than cold, and this trend is observed for several decades. In the middle of the last century in the United States recorded about the same amount of warm and cold extremes, in the 2000's record heat happened twice as often as record cold weather, in 2011 the ratio was 3:1, and in 2012 — 10:1, ie the tendency unabated.

Precipitation. In general, they were more in the United States, but the increase was mainly in the Northeast and Midwest, and in the form of heavy downpours. The first percentage of the strongest rains covers almost the entire country, but in the north-east of the rainfall has increased by 74% since 1950. In the Midwest — by 45%. This means that the extreme value, the case in earlier times two decades, there is now every thirteen years. Meanwhile, in the west and south-west of frequent drought. How much — hard to say, because to measure the degree of drought are not used standardized methods.

Extraordinary weather events become more frequent, too, but we should be careful, because in tornadoes and storms are very complicated relationship with the climate that we still do not fully understand.

Summing up, Mr Ueblz mentioned several recent events that are associated with exactly climate change. Among them — Texas drought, which was the result of changes in the 2-20 times more likely. Thus was made a logical transition to the next report, which is presented John Nielsen-Gammon University of Texas A & M.

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In summer, the U.S. has become noticeably hotter.

First, he recalled that in the late summer of 2010 through Texas took several tropical storms that moistened many parts of the state more than usual. The last of them collapsed on Sept. 27, and after three months in the eastern part of Texas came the dry season. Then there was recorded the windy spring in history, and by June 2011 all the spring flowers finally dried up. There was not a cloud that can reflect sunlight, no water, which removes heat by evaporation. The staff literally bake. The average temperature jumped by 1,5 ° C.

In some areas the temperature for more than 100 days reached to 37,78 ° C (100 ° F), which caused a fire. At its peak, this anomaly has covered an area corresponding to the size of Connecticut, Rhode Island and New York City. The amount of damage to agriculture is estimated at $ 7.6 billion

"To say that the drought is linked to climate change — it's all the same as saying that the plane crashed because of the force of gravity," — said Mr. Nielsen-Gammon. Yes, it's true, but it did not clear up. Among the specific causes of the drought climate models indicate La Ninyu — cold phase temperature fluctuations in the tropical Pacific Ocean, historically associated with a decrease in rainfall in Texas and surrounding states. But a La Niña was not enough to explain the drought in 2011.

When the researchers took into account the actual temperature of the sea surface, it appeared that what happened — not extreme value, although it is not common name. Although La Ninyu can still be regarded as the root cause of the drought, the strength of the latter is not associated with La Niney, and the general climate change.

What will happen next? Unknown. Fluctuations between La Niney and El Niño is very complex and changeable, and therefore to identify the long-term trend is not easy.

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The increase in the number of days with heavy precipitation over the mid XX century.

But the natural variability of climate is not the most difficult part of the climate science. It is much more difficult to deal with an ignorant public. This was at the meeting told Andrew Friedman Meteorological Organization of Climate Central, which among other things is responsible for the U.S. teleprognozy weather.

Previously, climate scientists have tried to explain the man in the street that a particular weather outside and climate — Things are different. But now the difference is erased. Last year was the hottest in 48 U.S. states. La Nina was the warmest in history. Australia had to add a new color to the color temperature scale to fix a new record. Arctic sea ice reached an all-time low in the era of satellite observations. Simply put, the man in the street is now able to observe climate change firsthand.

And public opinion began to change dramatically. Previously, scientists have criticized for "fudge", saying that there is no global warming, because we have snow fell in April. Now the rumor is running ahead of science: all, global warming has come — while scientists continue to be cautious. Sometimes the man in the street sees a trend where there is none. For example, sea level rise caused by warming, and indeed lead to more frequent floods like the one that brought the hurricane "Sandy. " But the Thai flooding that happened on the other side of the globe, was not caused by climate change and water resource management negligent upstream of the local rivers. And strong blizzard several days ago fallen to Boston, was a classic "Nord-Ost", which is not unusual.

The question, "Has the cause of the event global warming?" Correct to state: "How change Climate impact on the likelihood and extent of this event? "From the layman need to understand that climate — A thing more difficult than he imagines.

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Strengthening and weakening of the drought from 1958 to 2007.

On materials: Ars Technica
Source: Kompyulenta

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