Weatherdem's Weblog

Bridging climate science, citizens, and policy

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.


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.


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

  1. Dear Weatherdem,

    I am really sorry to hear about (and see) what is going on in Colorado; I do hope it comes to an end soon. Thanks for putting it all into context (in the way that the sensationalist – but perpetually-incredulous – daily TV news is not doing).

    Here in the UK, we have just had the wettest June (i.e. twice the long term average figure) since records began to be kept 102 years ago but, without doubt, so-called sceptics will point out the previous record was 100 years ago; and ask why June 1912 was so wet? What would your response be to this?

    On a more general note, why is it proving so hard for climate scientists to get the message across that increased frequency of extreme (wet, dry, hot and cold) events of increased severity was not only predicted by climate models; it is an inevitable consequence of increased moisture and heat in the atmosphere?

    Why is this point still getting lost in a fog-enveloped battlefield of reticence and ridicule surrounding any claim that an individual event may be attributed to anthropogenic climate disruption?

    • Thanks for the comment, Martin.
      Why don’t you ask a hard question once in a while? 😉

      More seriously, and without a lot of knowledge about UK precipitation records, I would say that twice the long-term average is within the range of natural variability. If it happened in 1912, then that’s a safe if rather nonfulfilling assessment. What would point to an anthropogenic fingerprint? Perhaps 3X the long-term average or something of that magnitude. The big problem with precipitation is it is so highly variable. It will be difficult to assign climate change as the causal factor in the type of drought that appears likely to occur in the coming decades because of the historical presence of multidecadal droughts over the SW US. That said, if the severity of the drought is much more than it has been historically, that would similarly provide a reasonable “fingerprint”.

      Climate scientists have done a poor job for a long time in providing salient and noteworthy communication on their topic of study. Skeptics have been “lucky” enough to leverage a disinformation apparatus that has been much more effective than the opposing view. They show little sign of actually taking that lesson to heart and doing something about it, although small-scale examples have been initiated in recent years to help stem the tide. The communication problem is a big reason why I’ve moved on from trying to convince people from a scientific viewpoint. People are better at understanding issues from an economic standpoint, so I say use that as an opportunity. Who doesn’t want to save, not waste, money? Nobody. So if you offer people easy solutions to save money, they’ll respond to that. Then it’s just a matter of building on that. Additionally, who doesn’t support technological innovation? Again, hardly anybody. So I think directing people toward supporting innovation is a key strategy. We’re not going to mitigate the climate problem away with our current set of technologies anyway, so it works on multiple problems at once. We have to move beyond despair and frustration, however. So the apocalyptic talk has to end, IMO.

      I would also say keep making the point that while not every incidence of an event can be directly attributed to anthropogenic climate change, the climate dice continue to be loaded, so we’ll see fewer 1s in the future and more 13s and 14s.

      Of course, we should keep conversing and reaching out to everybody we see who is interested in this topic. There are likely many success stories that we don’t point to as often as failures. I have come to the realization recently that there are a lot of smart people working on all kinds of aspects of this problem. They’re increasing our understanding of the problem day by day by day. That won’t stop just because skeptics challenge something we say on our blogs. 🙂

      • Thanks for all of that. Thinking about this some more, I think it becomes easier to argue that what we are seeing is not normal when one extreme is followed quickly by another of a different kind (e.g. floods and then drought in Texas). However, must we all go through hell to convince a few ideologically-blinded refusniks that they are mistaken…?

        I think the idea that one should use economics to focus people’s minds on why this is a problem we can no longer afford to ignore is commendable. However, our biggest remaining problem is that the economic arguments for inaction are also the most intractable and hardest to falsify (or so at least it would seem). Even when economists such as William D Nordhaus climb down off the fence and say we must tackle the problem, they are denounced by fake skeptics as having been bought by some supposed UN plot for worldwide Socialist government…

        In the meantime, I would like to be a technological optimist but I believe intellectual honesty demands that I not hide reality from people. However, I think Lester Brown may have just done me out of a job: This presentation (click on link below) pretty much summarises everything I have been saying about climate change and limits to growth… It is like Garrett Hardin, Paul Ehrlich, William Ophuls, Herman Daly and Jared Diamond all rolled into one…

      • Martin-
        Brown’s presentation is … interesting. However, IMO, It’s got some serious shortcomings.
        Talk of education is good. Talk of cheap, clean energy and water to every developing nation on Earth would be better.
        An 80% reduction of CO2 emissions by 2020 absolutely will not happen. It won’t happen by 2050 either – I’ll share more on that in a future post, but for instance, it’s quite easy to see that 2 million 2MW wind plants will not be installed by 2020 – not even close.
        Brown includes in Plan B a proposal to increase non-hydro renewables from ~4% of 2008 world electricity generation to ~60% of 2020 world electricity generation while simultaneously taking every coal, oil, and natural gas plant offline. As pro-renewable as I am, that task is quite simply impossible.
        Hence my conclusion that we will easily pass 400ppm CO2 concentration before 2020; also my conclusion that, in the near future, we are going to laugh at the idea of stopping warming at or below 2C. Large-scale change is on the way and I think we had better start planning for it. Again, I’m not trying to convince anybody of a doomsday scenario. But I think having a realistic expectation for the future will allow us all to act in accordance with the proper context, not a fantasy.

      • You have clearly gone into WOTE in more detail than me. Whilst I am 100% behind the logic of Brown’s analysis of the problem (perpetual economic growth cannot be the solution to all our problems because it is our ultimate problem). However, I would agree with you (and Grist blogger David Roberts) that 2C is no longer achievable (and I hope the IPCC will be brave enough to admit it next year). If Lester Brown thinks otherwise, he has allowed optimism to over-ride his realism.

        IMO, we are on target for 4 to 6C rise and CO2 of 450-550 ppm, simply as a result of inertia and governmental refusal to set a timescale for phasing out fossil fuel subsidies (let alone their use)… In the meantime, I get very annoyed with futurists and technological optimists because technology alone cannot save us; it cannot resolve Jevons’ Paradox… we cannot all spend all out time serving each other burgers and fries; and we cannot eat information, microchips, or money…

        However, even though I see Carbon Capture and Storage as a contemptable piece of fossil fuel lobby propaganda (i.e. addressing the symptoms not the cause of our problem), I admit we look likely to have to rely on it if humanity is to survive…

      • As usual, you provide substantial insight along with your opinion. You read a large variety of sources and can bring them to bear in discussion quite easily. Personally, I don’t know what I would do without Firefox bookmarks and even then I forget a great deal of what I’ve read on this topic.

        While we’re on the topic of predictions, I forsee 850-1200 ppm CO2, although I think I nearly agree with your temperature rise: 5C for sure, quite possible more. I too hope the IPCC is willing to put on paper that 2C is no longer attainable. That’s one reason I was happy to read about improved climate-language recently. I’m willing to give Lester Brown the benefit of the doubt, the presentation was clearly written a number of years ago. I have no idea whether he has shifted his opinion or not. I’m afraid you might be annoyed with me, because I’m left with the impression that technology is our best hope at this point of adapting and eventually mitigating the climate change coming our way. 😉 The political will has been present for quite some time, but I think the ingredient missing for substantial action is a viable political movement. The political establishment has to be presented with a legitimate loss of power before they respond to the real and present political will that exists among the masses.

        CCS and other strategies are all pieces of a larger puzzle, IMO. They all need to be harnessed if we’re to make headway.

        I appreciate the substantial discussion and look forward to additional exchanges in the future. 🙂

    • I wonder – does the UK experience generally wetter conditions during La Ninas or when they’re transitioning to ENSO-neutral conditions? Perhaps that is what happened in 1912. I would also look into the NAO/AO indices and the melting Arctic sea ice – perhaps there are feedbacks there…

      • I would be amazed if the UK’s weather is that much affected by what goes on in the Pacific. All the wierd weather we have had in the last few years seems to be dictated by the vagaries of the Jet Stream, which allows blocking High Pressure to being Siberian winters and off-track cyclonic systems to bring endless summer rain…

  2. Pingback: 8th Day of 100F+ Heat In Denver, CO « Weatherdem’s Weblog

  3. Pingback: Current & Future U.S. Heat Waves | Weatherdem's Weblog

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s