Global Warming Rolls Climate Dice Yet Again: High Amplitude Jet Stream Wave Brings Late July Melt Surge to Greenland

The old cliche is that lightning never strikes twice in the same place. In weather and climate terms, natural variability makes it highly unlikely that record year will follow record year, even when a forcing, such as human global warming, tends to push in that direction.

In the context of Greenland, it was very unlikely that record melt on the order of around 700 gigatons of ice lost during 2012 would repeat in 2013.  That said, even in a year like 2013, where climate attempts a return to the average trend line, it’s entirely clear that conditions are anything but normal.

Throughout late June and much of July, a downward dip in the Jet Stream dominated weather patterns over Greenland. Cold, Arctic air was locked over the massive island, pushing melt rates closer to ‘normal’ for a summer season. The term to use is definitely ‘closer,’ because even during weather conditions that would normally bring colder than average conditions to Greenland, warmth and melt were still above average.

Global warming adds a roll

A metaphor we can use to describe this phenomena of implied variability in a warming system is James Hansen’s climate dice. Imagine that a basic roll of a d10 gives us a typical weather pattern for Greenland. 1 on the dice represents record cold, 10 record warmth, 2 and 3 are colder than average, with 2 being near record lows and 3 being closer to average, 4, 5, 6 and 7 are average, 8 and 9 are hotter than average, and 10 is record heat.

This set of weather and climate possibilities is a basic representation of ‘normal’ for Greenland. But when we add in human climate change and global warming, we are essentially adding a new player to the mix, with its own set of dice. In this case, let’s add a 1d3 to the global warming hand. Now, with the extra dice roll for global warming, the potential for extreme hot, melting years just got far, far more likely and we begin to experience never seen before heat and melt events. But we still end up with colder than average years and normal years, just less of them.

The situation is probably worse than the simulation described above because on the typical 1 to 10 scale we can label 2012 about a 13 (with freakish never seen before record heat and melt) and 2013 through about July 26th a 7.1 — slightly hotter than average with ever so slightly above average melt.

The problem is that June and July were average when they should have been cold. I say this because a high amplitude wave in the Jet Stream flowed down over Greenland, pushing relatively colder air over the sea ice and into the freezer that is still Greenland. Such conditions usually push for colder than average Greenland temperatures and lower than average melt. This period of what should have been colder than average conditions instead resulted only in an abatement of record melt and a return to slightly above average melt.

Mangled Jet Stream switches back to ‘hot’

But now, even this brief respite appears to have evaporated. Over the past couple of weeks, the deep, cooler trough over Greenland eroded, weakening as warmer air pushed into southern Greenland. Now, the trough has completely reversed — becoming a ridge and somewhat mimicking the freakish conditions that occurred during 2012. So slightly above average melt conditions are now starting to swing back toward record melt conditions for this time of year.

You can see the large, high amplitude bulge riding from south to north, carrying air from the south-eastern US all the way north to Baffin Bay and southwestern Greenland, in the Jet Stream map for July 30th below:

Greenland Jet

(Image source: California Regional Weather Service)

This sudden Jet Stream switch brings back a weather pattern that caused such major melt conditions during summer of 2012 and such warm winter conditions for Greenland as 2012 turned to 2013. And the results, as far as ice melt goes, have been almost immediate. Earlier melt peaks at around 34% of the ice sheet during July were obliterated in one fell switch of atmospheric air flow that, once again, drew warm, temperate air into the Arctic.

Over the past two days, this extra warmth has increased Greenland melt area to above 40%, peaking at near 45% just a couple of days ago. This peak, though not as anomalous as the 90% + melt coverage experienced during early July of 2012, is still about 80% higher than the average melt peak observed for the period of 1981-2010 and more than double the average for melt in late July. It also puts Greenland further into above average melt year territory, possibly shifting the 2013 score from 7.1 to around 8.5.

You can see the melt coverages graph, provided by NSIDC, for the current year below:

Greenland Melt 2013 Late July

(Image source: NSIDC)

The warm air pulse that drove these anomalously high late season melt rates in Greenland appears to have settled in for at least the time being. Temperatures along the Greenland coast range from the upper 30s to the lower 60s — quite warm for this time of year — while summit Greenland is experiencing warmer than average temperatures in the lower 20s (Fahrenheit).

Above average melt when it should have been cold

So what is freakish about 2013 when compared to 2012 is not that it matched a major melt event that will likely stand as a record for the next five years or so, but that in a year where weather conditions would have pushed Greenland to be mostly colder than normal, above average warmth and melt were still experienced. In this case, it becomes very clear that we are rolling with loaded climate dice or, as the illustration above shows, human global warming is adding its own wicked set of rolls.


California Regional Weather Service


James Hansen’s Climate Dice

Learn about Dark Snow

Leave a comment


  1. Steve

     /  July 30, 2013

    I just came across an article in Rolling Stone about Jason Box and his concern about soot causing major albedo problems. Along with some microbes causing the same issue. Have you seen any reports were the soot from these Siberian fires is primarily landing? If a lot of it is landing on Greenland, any idea if it could have such a dramatic effect that quickly? Are the wildfires this year in the U.S. comparable to what we experienced last year? How alarmed would you be if Greenlaexperienced another surface melt like last year in the next few weeks? Am I correct in recalling that it was currently looked at as a 1 in 300 year event? I think that was from one of your posts over the last couple weeks.


    • Oh that soot and smoke is still mostly over Russia and Europe at the moment. It will probably circle the northern hemisphere for some time. Some of it will probably end up on the ice, though.


  2. Steve

     /  July 30, 2013

    I just started posted on here recently, but I’ve been looking at things like this over the last few years. Is it me, or have new events and information been popping up at an unbelievable pace this year? There is nobody that I know that has any interest in the details of what we are seeing. Sorry to keep peppering you with questions.


  3. Steve

     /  July 31, 2013

    I’m in insurance and what I’ve seen the last three years is statistically disturbing to say the least. Here in Illinois, which has probably fared better than most states, we are seeing companies’ catastrophe annual projections increase by 500% when compared to historical losses between 1973 & 2003. The property insurance field is in for some very ugly changes in the not too distant future.


  4. Steve

     /  July 31, 2013

    Water back-up in basement from sump pumps being overwhelmed or power loss(that doesn’t even take a flood), hail damage to roofs, & wind damage. There has only been one bad tornado that I can recall in the state that did a lot of damage to a small town in southern Illinois. I don’t see FEMA’s loss numbers for floods. But we have had a lot of that as well and that isn’t factored into the number I listed.

    Rates have gone up a lot, but they haven’t increased like they statistically should. I’m glad they do, but I don’t know why these companies still want new business in an area that is losing money. I’m still waiting for the BIG change that hasn’t hit yet. Just a matter of time. It would hurt the housing market badly right now if these companies reacted like they statistically should right now.

    My big worry is actually snow. When a heavy populated region get hits with a 40 inch snowfall and roofs can’t handle the snow, it will hit the fan. Hail is concern #2 IMO. A major hail storm across a huge metro area could be devastating.


  5. Steve

     /  July 31, 2013

    Catastrophe losses are a defined type of loss. I don’t know what percentage they typically make up of a companies total losses. These are events that affect a high percentage of homes in a given area. Smaller insurance companies actually purchase insurance from bigger insurance companies to protect themselves for these kind of events. So rates shouldn’t go up by 500%. But if catastrophe losses make up 33% of losses for a company, that should almost cause homeowner rates to double or make changes to minimiz their risk in the future.


    • Fantastic information here, Steve. Definitely something to chew on and a clear illustration of how we are so dependent, economically, on a stable climate. My opinion is that a part of adaptation will involve no longer building in certain areas. The problem is that, without mitigation, dangerous regions just spread and spread. If you start to hit Heinrich type events, the weather can get very, very nasty (far worse than now).

      So how are the re-insurers holding up?


  6. Steve

     /  August 1, 2013

    Maybe my regional carrier that I see the internal losses for isn’t as good of as an indicator as I thought. Either that or there has been a lot more hail damage here in Illinois then many other states. Here is an article from the NYTimes from May talking about it. Re-insurers are obviously big proponets of climate change and making changes. Interesting short article. They report slightly less than a 50% increase when compared to a decade ago. The numbers that I was given for my regional carrier compared now to 1973-2003, so it makes it hard to compare the two. Either way, it is a big problem, that is going to get much worse and will have a bigger and wider impact than most realize.


    • I’d seen the NYT report, which is why your figures are so shocking to me. NOAA shows storm damage is definitely up for the US and the big reinsurers seem worried sick about climate change.

      I’ve often wondered if regions in flood plains or coastal areas like Miami would undergo a kind of forced housing migration as insurers refuse to cover certain areas or only offer coverage for such areas at very high rates. Although, I think the rate of climate change we are seeing, unfortunately, will outpace any kind of movement spurred by that kind of industry response.


  1. Greenland Ice Sheet Slipping Under Hottest Temperatures Ever Recorded | robertscribbler
  2. Another Week of Climate Disruption News, August 4, 2013 – A Few Things Ill Considered

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

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: