7th Day of 100+F Heat In Denver, CO; June 2012 Hottest On Record

It’s official: June 2012 was the hottest June on record in Denver, CO (dating back to 1872) with an average temperature of 75F, 7.6F above normal!

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.

Context

Last year, there were 50 consecutive days of 90F+ maximum temperatures at Denver, which tied for 9th-longest in our recorded history.  With 7 additional days, it would have been the 3rd-longest streak; 11 more days would have tied the longest streak on record, set in 2000.  Note also that 6 of the 11 longest streaks have occurred in the 21st century!  Normally, Denver experiences ~34 days of 90F+ maximum temperatures.

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.

Millions of people are currently without power (due to violent thunderstorms) and are experiencing 100F+ temperatures in the eastern US.  How many more summers like this do they want to have?  They’re going to find out, that’s very nearly certain now.

MIT Doubles Previous Warming Prediction to 5.1°C

The nice part about science is the ability to retest things as new data and better methods become available.  In the case of climate change, new data and updated models are producing increasingly higher warming predictions for the end of this century.  MIT joined other entities in retesting their predictions with their Integrated Global System Model .  The IGSM is used to make probabilistic projections of climate change from 1861 to 2100.  Back in 2003, at the time of their original predictions, end of the century median surface temperatures were 2.4°C higher than the climatological average of the preceding century.  Armed with additional data and significant updates to the model, their latest prediction is an astounding 5.1°C (median value) in the 2091 to 2100 time period.  That’s more than double the value found just a handful of years ago.  I can guarantee, and I’m sure they would agree, that their data isn’t completely sufficient; nor is their model accounting for critical feedback processes, many of which we’re only now becoming aware of.

Their new study also includes new predictions of CO2 concentrations over the next 80 years.  Their new 5th percentile projection is higher than their 2003 median (50th percentile) at just under 700ppm (current values are 387ppm and increasing).  Their new 50th percentile projection is almost as high as their 2003 95th percentile projection: 866ppm vs. 900ppm.  Finally, their new 95th percentile projection registers at a nearly unfathomable 1100ppm.  Concentrations of CO2 leading up to 1100ppm would certainly open the door to out-of-control climate feedback processes, the kind which nobody would want to deal with.

Warming in their simulations range from 3.1°C to 7.3°C by 2100.  They make sure to note that not one of their 400 simulations resulted in globally averaged temperature increases of less than 2°C.  Not one.  That’s a very significant result.  Why the big change?  The authors explain:

Rather than interacting additively, these different affects appear to interact multiplicatively, with feedbacks among the contributing factors, leading to the surprisingly large increase in the chance of much higher temperatures.

That multiplicative description is characteristic of non-linear systems, such as the climate system.  It’s quite frankly something that many climate change deniers/delayers don’t understand or gloss over.  Additive changes of GHG emissions result in multiplicative surface temperature changes down the road.  We don’t have to inject too much CO2 or other gases to generate large temperature increases.  Which little additive change in emissions will result in more feedback processes kicking in?  We don’t know.  As such, I don’t think it’s worth it to continue emitting GHGs until we see the feedback has kicked in – it will be too late to slow things down at that point.

Another important result: polar amplification is present in their simulations.  By that, I mean that just as has already been observed in the past 30 years, polar temperatures are expected to increase more than temperatures across the mid-latitudes and tropics.  There are some differences between the Northern and Southern Hemispheres.  Their median percentile projection calls for a 10°C rise at the north pole by 2091-2100 compared to 1981-2000, a 7°C rise at 45°N and a 6°C rise at the Equator.  At 45°S, the median temperature change is predicted to be slightly more than 4°C; the south pole temperature change is predicted to be about 7°C.

Does anybody think the Arctic ice sheet can exist year round with 10°C warmer annual temperatures?  I certainly don’t.  This report identifies a 5% probability of Arctic Ocean ice disappearing in the summer by 2100.  I don’t think it will take until 2025 before that happens.  Again, the poles are observed and sampled very infrequently in time and space.  We simply don’t have solid ideas of how polar climate dynamics behave – not in stable conditions and certainly not in unstable conditions.