The drought/extended heatwave this year from the front range of the Rockies, east across the central and southern plains and Ohio Valley will soon prove to be as bad, or worse, than the greatest one since the "european" conquest 200+ years ago. This exceptional drought, which occurred from 1932-1936, was what brought us the term "dust-bowl", from the dust/windstorms which eroded the drought-stricken lands of topsoil in those drought years of the 1930s.
This historic map of the Palmer Drought Severity Index (PDSI), percent of time in severe/extreme drought, tells the story. the western central and northern plains and parts of the intermountain-west, were locked in severe and extreme drought conditions 50 percent of the time, in the years 1934-39.
Failure of the corn crop is/will be occurring this year across most of this same area, and even further east, it seems likely. This will cause food prices to greatly increase during the next several months, and year, nationally, and internationally.
http://www.commondreams.org/view/2012/07/26-5
This will produce great, and unfortunate consequences throughout the World, which will be made even worse by rampant speculation in the commodities markets, which drive prices up much further than they would otherwise be, and hence, condemn many millions more globally to suffering and starvation.
http://www.commondreams.org/view/2012/07/26-5
This will produce great, and unfortunate consequences throughout the World, which will be made even worse by rampant speculation in the commodities markets, which drive prices up much further than they would otherwise be, and hence, condemn many millions more globally to suffering and starvation.
The basic weather pattern causing this, which we'll discuss later, looks likely to continue for at least a few more weeks, if not longer. And which, some people think, is causing many people living in these areas to rethink their positions on global warming, which could have interesting consequences.
An excellent summation of this unfortunate and far-reaching slow-motion disaster comes from the folks at Climate Central, a great resource for the latest global warming research/description of current events.
http://www.climatecentral.org/news/extreme-heat-proves-relentless-in-central-states/http://www.climatecentral.org/news/ongoing-coverage-of-historic-drought-in-us/
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2158
Extreme Heat Proves Relentless in Central States
High temperature forecast for Tuesday, July 24, showing the area of extreme heat in the central states. Click on the image for a larger version. Credit: NOAA.Through July 21, St. Louis and Columbia, Mo., had each set a record for the warmest year-to-date, beating a record established in 1921. The National Weather Service said that by October, the records for the maximum number of days with a high temperature of 90°F or greater, and 95°F or greater, "will also likely be threatened at all three of our official climate locations."
Further west, it is possible that North Platte, Neb., will wind up with its second-longest streak of consecutive 100°F days, with nine such days if temperatures reach the century mark through Wednesday.
North Platte, which sits along I-80 in the western part of the state, had already seen 16 days this year with temperatures of 100°F or higher as of July 23, including 12 100-degree days in July alone. The all-time record is 29 such days, set during the Dust Bowl year of 1936. Omaha has had its fourth-longest streak of consecutive days with high temperatures of 95°F or greater, and has hit 100°F or higher five times this month. The high temperature on both July 22 and 23 was 105°F, which were record daily highs. Omaha normally averages just two 100-degree days during July.
During the July 17-to-23 period, 866 daily high temperature records were set or tied across the country, along with 716 warm overnight low temperature records. Of these, 14 of the high temperature records were monthly records, and eight were all-time high temperature records. So far this year, warm temperature records have been outpacing cold records by a ratio of about 7-to-1. The ratio is even more lopsided, at closer to 9-to-1, when looking only at record daily highs compared to record daily lows. (Track record-breaking temperatures using Climate Central's Record Tracker.)
In recent years there have been many more warm temperature records set or tied in the U.S. compared to cold temperature records, part of a longer-term trend. Credit: Climate Central.As the climate has warmed during the past several decades, there has been a growing imbalance between record daily high temperatures in the contiguous U.S. and record daily lows. So in the coming decades, we may see more and more of these record-breaking temperatures in cities across the U.S. A study published in 2009 found that rather than a 1-to-1 ratio, as would be expected if the climate were not warming, the ratio has been closer to 2-to-1 in favor of warm temperature records during the past decade (2000-2009). This finding cannot be explained by natural climate variability alone, the study found, and is instead consistent with global warming.
The heat in the Central states is compounding drought concerns, as one of the worst droughts in U.S. history has intensified during recent weeks due to the combination of record warmth and well below-average rainfall.
Further north, though, some beneficial rain is falling in a zone from Minnesota through northern Illinois, Michigan and Ohio. A frontal boundary marking the dividing line between cooler and less humid air to the north, and the extreme heat to the south, has already sparked one round of severe thunderstorms on Tuesday. A long-lasting, fast-moving complex of thunderstorms producing widespread damaging winds (similar to but not quite meeting the official criteria of a "derecho") — tore through the Chicago area, knocking out power to as many as 175,000 people.
More severe weather is expected during the week, but most of the rain from these thunderstorms is likely to fall to the north of the areas most heavily affected by the drought.
The central/eastern US drought is not the only significant global-warming issue at hand currently, however.
Amplified warming and melting of the entire greenland ice sheet means surface meltwater will pool and eventually sink through large areas of it, lubricating the bases, with unknown consequences. Large meltwater pools have been identified in recent years in some areas of the ice sheet, which have been measured to flow down to the base rocks below the ice. What is not known at this time, is how much water it will take lubricating the bases of these massive glaciers/ice sheets, before large chunks of them break off and slide into the surrounding seas, which would then cause rapid global sea level rises of several feet, and for the bulk of the Greenland Ice Sheet, at least eight metres (27 ft).
This amplified melting of the Greenland Ice Sheet has been the basis for a few of our future projections of conditions decades hence across North America. The main point being that research has indicated that the last time atmospheric CO2 levels were as high as they are now, 390 ppm (from naturally occurring volcanism) 250,000 years b.p., sea levels were 6-9 metres higher! And we are projected to reach 500 ppm, in less than 40 years.
In addition, the summer arctic sea ice coverage, is once again at record low-levels, and getting thinner every year, heading toward summers in which no sea ice is left in the Arctic, within a decade or so, if not sooner. Which would be a strong "positive feedback" mechanism, enhancing warming throughout the Arctic, and the rest of the World, as the darker sea surface absorbs tremendous amounts of heat energy from the sun, during the summer, instead of the sea ice, which reflects more than 80% of incoming solar radiation. Which in turn will cause larger areas of methane and CO2 to be released from thawing permafrost and shallow Arctic Ocean seabeds (especially north of the Eastern Siberian coastline).
So, given these extreme drought/heat waves that are occurring from the western great plains of the US lower 48, east into the Ohio Valley, what is the basic mechanism responsible for this?
The plot, above, is of the mean 500 mb heights for June 2012 across North America. A quick recap, meteorologists track weather systems at several levels in the atmosphere. The height at which the atmospheric pressure is a standard level, is proportionate to temperature. Lower heights at 500 mb (which is generally between 4850 and 6000 metres across the globe on any given day in winter/summer) mean a colder airmass, as cold air is heavier, and less dense, than warmer air, and hence occupies less physical volume/height. So when you hear the term "high pressure ridge", meteorologists are usually referring to higher 500 mb height values bulging poleward, moving warmer air north (or south in the southern hemisphere). 
The plot above, is of the mean 500 mb heights for the 30 year period 1991-2011. 500 mb heights are 300-500 metres higher this June, than over the 30-year composite mean. A "higher-amplitude ridge" centered over the southwestern states has amplified north over the southern and western plains. Hence, this area of hot dry air, caused by large scale subsidence aloft of air pushed poleward from tropical convection (showers/thunderstorms) is further north and "sharper" than the average conditions over the past 30 years. Generally speaking, it is these "higher amplitude" jet stream flows that are bringing greater warmth further poleward, that are amplifying warming across the Arctic, as we've mentioned before.
At the same time, globally speaking, the "jet stream", which is the band of strong winds aloft that move low pressure systems that form due to the contrasts of polar vs. tropical/subtropical air, is moving further poleward, as the global atmosphere warms. Hence, stronger ridging that used to be say over the latitudes of 28-38N, and further to the west, over those latitudes in North America, are/will continue to expand poleward and amplify. This year, 2012, it looks like the jet stream over the southwest and central US has moved about 4-5 degrees northward, from the composite mean.
A more "highly amplified" jet stream has also had it's effects here in Alaska, as the above charts show. Here we can see that during the month of June (and July has been quite similar so far), a stronger and deeper area of low 500 mb heights has been present over the Gulf of Alaska, and lower 500 mb heights across the rest of the state.
In fact, so far this month in Anchorage, it's been the 2nd coldest in its 90 year period of record. Rainfall has been above average as well, but not to record levels. What has this meant for us here in South-Central Alaska?
Well, as here at just 1100 metres off the Crow Pass trail around Crystal Lake, our record snowfall of the past winter
is still in the process of melting, as of last week, and only 1/3 of the ice on Crystal Lake has gone out.
In addition, the majority of the days of this past June and July, have been cool and cloudy, and often, in our daily runs into the Chugach
Range, the cloud bases drop below 500 metres, with drizzle and light rain.
There was still alot of snow on the margins of the Raven Glacier, just on the other side of Crow Pass, this past week, so we will take our annual comparison pictures as scheduled the first week in September, to document the changes on this easily-accessible lower-elevation source-region (2000 metres) glacier.
And which we will continue to do, as long as we are able.
While it has been a cool and cloudy, often wet, summer so far in South-Central Alaska, we are not too worried. Because we know, as the climate continues to warm due to our uncontrolled emissions of CO2 and methane (CH4), even our cooler summers, will slowly warm, here in South-Central Alaska, as the basic jet stream flows continue their poleward progression. In fact, in 40 years, our summers overall here, will be somewhat warmer. But we do worry quite a bit about our winters, they are becoming more turbulent, and potentially hazardous in some ways. More heat energy available in winter from the warmer Pacific Ocean, and subtropical airmasses being pushed further north, and interacting with the cold Arctic air flowing out from the interior, are/will be fueling more frequent, stronger storms. Which already can be damaging around the Anchorage "Bowl".
There is no escaping our changing and warming climate, due to fossil fuel extraction/use, no matter where you live. Cheers.
