Biblical Floods in Colorado

You've probably been hearing about the epic-Biblical-thousand year floods that Boulder, Colorado is experiencing. The cause is record rainfall - as you can see from the chart, above, developed by Climate Central. In fact, according to Weather Underground and Climate Central, Boulder, which normally gets 1.7 inches of rain in September and 20.68 for the year, got half a year's rain in less than half the month of September. (The forecast has a small chance of rain today, and then sunshine for the next few days.)

What might be causing all the rain? The Pacific. According to Climate Central:

During the past couple of weeks, the weather across the West has featured both an active Southwest Monsoon and a broad area of low pressure at upper levels of the atmosphere, which has been pinned by other weather systems and prevented from moving out of the region. It was this persistent low pressure area that helped pull the moisture out of the tropics and into Colorado. Signs point to the tropical Pacific being the source of the abundant moisture according to the University of Wisconsin’s Cooperative Institute for Meteorological Satellite Studies. From there, the moisture plume was transported northeastward, over Mexico and into Texas, and then northward by upper level winds.

This tropical air mass, which is more typical of the Gulf Coast than the Rocky Mountains, has been forced to move slowly up and over the Front Range by light southeasterly winds. This lifting process, known as orographic lift, allowed the atmosphere to wring out this unusually bountiful stream of moist air, dumping torrents of rain on the Boulder area for days on end.

That's a screen shot of the satellite images loop CIMSS released showing the tropical air mass. (I couldn't find it to embed it, but click on the link to Climate Central - you can see it moving there.)

Is climate change involved? No one weather event can be traced back easily to climate change, but there is at least one suggestive factor: the magnitude of the change from past events. And, of course, temperatures are rising around the globe. Generally, warmer temperatures mean more water vapor in the air, which means more extreme rain or snowfall. Stay tuned.

It's official: 2012 hottest year on record

You've probably read news reports yesterday and today stating that 2012 was the hottest year on record in the contiguous United States. You can find NOAA's original release here. Here's part of the discussion:

The above-average temperatures of spring continued into summer. The national-scale heat peaked in July with an average temperature of 76.9°F, 3.6°F above average, making it the hottest month ever observed for the contiguous United States. The eighth warmest June, record hottest July, and a warmer-than-average August resulted in a summer average temperature of 73.8°F, the second hottest summer on record by only hundredths of a degree. An estimated 99.1 million people experienced 10 or more days of summer temperatures greater than 100°F, nearly one-third of the nation’s population.

 Just how hot was it?  Climate Central has developed an interactive graphic showing the changing temperature in each state. The screen shot shows a graph of Iowa's increasing temperatures over the years since records have begun (yes, I know the graph should start at 0 (or 32, since we're talking about temperatures measured in Fahrenheit, but I'm letting it go in this case).
 
2012 was also the second-most tempestuous year. According to NOAA:

The U.S. Climate Extremes Index indicated that 2012 was the second most extreme year on record for the nation. The index, which evaluates extremes in temperature and precipitation, as well as landfalling tropical cyclones, was nearly twice the average value and second only to 1998. To date, 2012 has seen 11 disasters that have reached the $1 billion threshold in losses, to include Sandy, Isaac, and tornado outbreaks experienced in the Great Plains, Texas and Southeast/Ohio Valley.

Extreme weather and ocean salinity

Illustration from Climatecentral.org

Climate Central has posted a very clear explanation of the new research using changes in ocean salinity to stand in for worldwide drought and rainfall measures. The idea is straightforward: with climate change, extreme weather cycles are likely to worsen. We're starting to see that regionally, but regions - even ones as large as a continent - are too small to give a global picture. Hence the move to measure ocean salinity. (No one has rainfall data over the ocean, so salinity serves as a proxy measure.) As you can see from the map above, ocean saltiness is increasing. And what's really news is that it appears that the change is happening about twice as fast as the land-based predictions had suggested.