While 90°F might sound like a low threshold for many across the US Midwest, the total number of 90°F days for Denver in 2012 is racing for the record books. An average year yields 32 90°F days in Denver – or at least an average year in a cooler climate.
Through the 26th of July, 2012, Denver, CO has recorded a total of 41 days of 90°F+ maximum temperatures. Wednesday was the last day that could have registered a sub-90°F temperature, but 90°F was the recorded high for the day. As such, the latest streak of 90°F+ days continues: 16! That streak edges out the 15-day streak Denver already recorded earlier this summer. So not only have temperatures been warmer than normal more often than normal, they’ve been warmer than usual for extended periods of time. That means that ecosystems haven’t had their normal chance to recuperate from such high temperatures – a point that I will spend more time on in an upcoming post.
That streak is likely to continue: the forecast for the next 7 days includes highs in the mid- to upper-90s. Denver could witness a July with only 4 days below 90°F. So far this month, the average temperature departure from average is +4.7°F. That isn’t as high as June (+7.6°F), but the general trend is clear: 2012 is very warm for Denver, CO and other locations across the mid-section of the US.
Denver has also now recorded 38 days of 90°F+ days, so only 12 more such days need occur the rest of this year to make the top-9 list.
Denver is also in the midst of another consecutive 90°F+ day streak: 13 through yesterday (11 Jul – 23 Jul). That is in addition to the previous 15-day streak the city recorded from late June through early July. The streak will continue through today before slightly cooler temperatures (only 89°F?) occur Thursday, then right back into the 90s starting Friday.
The thought of autumn and cooler temperatures is very appealing.
Through the 19th of July, 2012, Denver, CO has officially recorded 10 days of 100F+ maximum temperatures. The previous year with such heat was 2005, when 7 such days were recorded. Due to Denver’s latitude (~40N) and altitude (~5,200 ft. above sea level), 100F days are rare. This year is developing a series of very anomalous heat and drought observations.
Denver typically experiences 32 90F+ days per year. With most of the summer still to go, Denver has already surpassed that mark. It appears the city is targeting the top-10 90F days in a year. That record is held by 2000 when there were 61 days of 90F maximum temperature or higher. Note that six years since 2000 populate the top-9 list: 2000, 2002, 2005, 2006, 2007, and 2011. There are only four years prior to 2000 in the top-9 (three are tied for 9th): 1994, 1978, 1964, 1960, and 1874. The 9th place years recorded 50 90F days.
So far in 2012, there were 2 90F+ days in May, 17 in June, and 15 so far in July, for a year-to-date total of 34. Denver likely recorded an additional 100F day today and will do the same thing tomorrow. The extended weather forecast doesn’t call for a high less than 90F for the next 7 days. Beyond that, above-average temperatures are forecasted for both the next month and the next 3 months. 90F daily maxima are not unheard of in the first couple weeks of September and I don’t at this point expect conditions to be cooler than that this year.
15 consecutive days were 90F+ from the 22nd of June (102F!) through the 6th of July. If all those records hold up to quality control, that should tie for 7th on the list of most consecutive days with 90F or higher:
Notice how the majority of these dates begin in July, not June. Note further that there were three other times when such a streak began within one day of June 22nd (see full list). The reason the streak stopped on the 7th of July was a temporary appearance of North American monsoon moisture that made its way from the Gulf of Mexico around the western periphery of the massive high pressure system that is at the heart of the record setting heat wave and drought afflicting the US this year.
So: will 2012 challenge 2000 for the most 90F days in one year? There are only 16 more days before Denver makes the top-9 list, then 11 more to tie for 1st place. This isn’t a record most of us want to see happen, of course. I would much rather see the monsoon return with a vengeance and alleviate the precipitation deficit under which the area is suffering this year.
Will another noteworthy consecutive 90F streak occur? Denver has 9 in a row through yesterday. With today’s likely 100F, another streak of 10 joins the list. As mentioned earlier, conditions don’t look like they’ll change any time soon. 2012 could see two extended streaks of 90F+. Stay tuned.
Yesterday’s high of 101F added to the total number of days of 100F+ temperatures: to date, there are now 7. Last week, there were 5 days in a row of 100F+ heat, matching the all-time record for Denver. The streak included 2 105F readings, which tied for the all-time hottest temperature recorded for Denver. There was also a 100F+ reading a few days prior to that streak. For completeness, I want to point out that the 27th through 30th of June weren’t much cooler: it was 97, 97, 98, and 99 on those four days, so we didn’t miss 100 by much.
Here are a few pictures demonstrating the intensity and extent of the heat that not only affected Denver, but much of the High Plains prior to the impacts east of the Mississippi over the weekend:
Figure 1. Contour plot of surface maximum temperatures for July 1, 2012.
Figure 2. Plot of surface maximum temperatures by station for July 1, 2012.
Figure 3. Contour plot of surface maximum temperatures for June 30, 2012.
Figure 4. Contour plot of surface maximum temperatures for June 29, 2012.
Figure 5. Plot of surface maximum temperatures by station for June 26, 2012. This is one of the two dates that Denver’s temperature tied for the all-time recorded high of 105F.
So far this year, we are in the middle of a 10-day streak. Today, the temperature has already been over 90 for over 4 hours (now 2:30P local) and the forecast calls for 90F+ for at least the next 5 days.
I couldn’t find records on the average number of 100F days in Denver in a year. I would venture a guess and say that is because the number is less than one. I’ll do some more digging and see if I can find out one way or the other.
Climate Projections
It wasn’t that long ago that I first saw projections of potential future climate maps for the US and didn’t think I could imagine what it would be to live through such conditions. I’m sure there are many people who either similarly couldn’t imagine it because it hasn’t happened yet or who are simply unaware of such projections. Take a look at the following graphic:
Figure 6. Projection for 2090-2099 of the number of weeks per year where maximum daily temperatures exceed 100F. This projection used the A1FI SRES scenario, which best represents the globe’s current emissions path.
For the sake of conversation, I will assume that Denver has so far this year experienced 1 week (7 days) of 100F+ temperatures, and will further assume that no additional 100F days will occur in the rest of the year. Under the A1FI scenario, by the end of this century, such a year would be considered relatively cool!
This shift toward more extreme temperatures can also be represented in this graphical manner:
This graphic shows that the increase in average temperature does not have to be that large in magnitude in order for a sizable number of events at the tail of a distribution (e.g., temperature) to occur.
While Colorado’s weather this summer shifted from warm to wet to hot, it was plain and simply nothing but hot, hot, and hot in the states to our south. How hot was it?
It was so hot that Texas and Oklahoma set the U.S. record for the 1st and 2nd hottest summers: 86.8F and 86.5F, respectively, beating out Oklahoma’s 1934 record (set during the Dust Bowl years) of 85.2F. To be clear, from June through August, the average of all the temperatures taken at the top of every hour came out to above 86 degrees. Oh, Louisiana’s 2011 summer now ranks 4th warmest all-time at 84.5F.
When records from the previous hottest period in the nation’s history are falling, it’s time to pay attention. Instead of natural variability playing the primary role, the heat wave this year was by the altered background state.
Statistically speaking, it is more significant that Texas set the record instead of Oklahoma. The number of weather stations in Texas is obviously much higher than those in Oklahoma. Most, if not all of those stations were subjected to similar conditions for 3 months in order to set this kind of record – a truly amazing occurrence.
I’m going to riff off of Joe Romm’s recent post on a similar topic and re-post some graphics I’ve written about before. They are particularly salient now that the summer of 2011 is fresh in our memories.
This is a plot from a NOAA-led report that shows what the future holds under a business-as-usual emissions scheme. Focusing in on Denver, which just experienced its hottest August and 3rd hottest month ever with 22 days above 90F maximum temperatures, puts this plot into some context. Denver didn’t record a single 100F degree day this year. But if we continue along the path we’re on much longer, we’re likely to experience 7 to 9 weeks of 100F or hotter days. Moving on down to Texas and Oklahoma, things really get cooking. Between 13 and 23 weeks of 100F or hotter days are in their future. How much agriculture do you think can be successfully supported in those conditions? How much ranching can be done? How many water pipes will break in the ground as that ground swells in the heat?
And it’s not just heat, as this plot from a recent NCAR study demonstrates. Palmer Drought Severity Index values in the 1930s spiked very briefly to -6 (see scale above), but rarely exceeded -3 during the rest of the decade. By the 2030 decade, projections of -4 to -6 PDSI values cover most of the American Southwest. Texas gets off “easy” with PDSI values holding near -2 for the decade. Significantly higher temperatures in twenty years’ time accompanied by drought conditions worse than those of the Dust Bowl could easily be the future that comes to pass.
Given the scope of the tasks facing us: reduction of emission levels that are currently growing and deployment of infrastructure and technologies to do so, I’m not optimistic that we can turn things around in time in order to avoid these kinds of scenarios. Given the severity of the scenarios, we had better start doing something substantial soon.
The main focus of this message is meant for Sen. Majority Leader Reid, but applies to anyone who is either actively working to prevent any energy or climate legislation from passing Congress or is offering up mealy-mouthed whines about how hard it is.
The climate doesn’t care, Sen. Reid. It doesn’t care about your chamber’s absurd set of rules; about how many votes you do or do not have; about your re-election campaign; about any political process or effort to fawn to the media.
The climate simply responds to forcing, of which humans have done and continue to do plenty of.
Think action on climate change is hard, Sen. Reid? Ask the Russians how hard their worst heat wave in recorded history was earlier this year. Ask the Pakistanis how hard the floods are making their lives. Ask some Africans how hard it is to feed and water their families when record drought continues to strike the region. Those folks are dealing with the industrialized world’s greenhouse gas pollution. Their lives are not only being made harder, but in a growing number of cases, impossible.
I’m sure they’ll all feel much more comfortable, and perhaps their lives will all get easier, as soon as they hear you might take up climate and energy issues piecemeal, because dealing with them in all their complexity is just more than you and your colleagues can seem to manage.
We’ll deal with this issue when we’re forced to and not much sooner, as I see it now. By then, of course, the costs associated with it will have skyrocketed and whatever actions we take will be less effective than they would be if started today. But Sen. Reid and others will have kept their hands on power as long as they possibly could along the way. That’s the truly important part to this story, after all.
