Arctic Sea Ice

2016 SIPN Sea Ice Outlook: June report

The first Sea Ice Outlook of this year has been published. The SIO is organized by the Sea Ice Prediction Network (as part of the Arctic research program 'Study of Environmental Arctic Change', or SEARCH), and is a compilation of projections for the September 2016 Arctic sea ice extent, based on NSIDC monthly extent values. These projections are submitted by professionals as well as amateurs (public outlooks).

Here's the summary for the June report:

The distribution of Outlooks for statistical and dynamical models have a median extent that is 0.15 million square kilometers different from each other, with a slightly larger spread for the statistical models than the dynamical models. The same sort of spread difference was seen in 2015. Separating out fully-coupled dynamical models from ice-ocean models shows that fully coupled models give a slightly lower forecast with a median of 4.57 versus 4.62, yet have a larger spread (Figure 2). The median forecast of heuristic forecasts is 4.0 million square kilometers and the spread is small. However, actual contributions to the two polls show a diverse range from 2.9 to 5.3 million square kilometers.

The overall width of the distribution of Outlooks has narrowed compared to last year: the interquartile spread across all types of contributions is 0.53 million square kilometers, which is a decrease of 0.27 million square kilometers since last year. The overall range is also reduced to 3.4 to 5.23 million square kilometers.

And here's the figure showing all the projections (click for a larger version):

2015 SIPN Sea Ice Outlook: July report

The second Sea Ice Outlook of this year has been published. The SIO is organized by the Sea Ice Prediction Network (as part of the Arctic research program 'Study of Environmental Arctic Change', or SEARCH), and is a compilation of projections for the September 2015 Arctic sea ice extent, based on NSIDC monthly extent values. These projections are submitted by professionals as well as amateurs (public outlooks).

Here's the summary for the July report:

The median Outlook for September 2015 Arctic sea ice extent is 5.0 million square kilometers (km²), which is the same as the June Outlook median. The quartile range is 4.4 to 5.2 km² (see Figure 1 in the Overview section, below). Contributions are based on a range of methods: statistical, numerical models, estimates based on trends, and subjective information. The overall range (excluding an extreme outlier) is 3.3 to 5.7 million km². The median Outlook value is up from the July 2014 median value of 4.8 million km². These values compare to observed values of 4.3 million km² in 2007, 4.6 million km² in 2011, 3.6 million km² in 2012, and 5.3 million km² in 2014. In general, the heuristic approaches forecast a mean September extent around 4.1 million km², whereas the statistical and dynamical modeling approaches both suggest mean September extent near 5.1 million km², with the dynamical modeling contributions showing a narrower range.

The lack of significant change between this month and last is largely related to the fact that most contributors did not change their forecast for July. Another factor could be the lack of significant atmospheric or oceanic forcing that would result in a large change from the June forecasts. A discussion of 11 dynamical model contributions shows no major differences compared to last month's report. This month's report also includes results from three regional predictions and a discussion of current ice and atmospheric conditions.

Read the entire report here.

And here's the figure showing all the projections (click for a larger version):

The September minimums for the last 10 years (in millions km2, found here):

2015 SIPN Sea Ice Outlook: June report

The first Sea Ice Outlook of this year has been published. The SIO is organized by the Sea Ice Prediction Network (as part of the Arctic research program 'Study of Environmental Arctic Change', or SEARCH), and is a compilation of projections for the September 2015 Arctic sea ice extent, based on NSIDC monthly extent values. These projections are submitted by professionals as well as amateurs (public outlooks).

Here's the summary for the June report:

The median Outlook value for September 2015 sea ice extent is 5.0 million square kilometers with quartiles of 4.4 and 5.2 million square kilometers (See Figure 1 in the full report, below). Contributions are based on a range of methods: statistical, numerical models, estimates based on trends, and subjective information. We have a large spread in the Outlook contributions, which is not surprising given the wide-ranging observed values for the September extent in the past few years. The overall range (excluding an extreme outlier) is 3.3 to 5.7 million square kilometers. The median Outlook value is up from 4.7 million square kilometers in 2014. These values compare to observed values of 4.3 million square kilometers in 2007, 4.6 million square kilometers in 2011, 3.6 million square kilometers in 2012 and 5.3 million square kilometers in 2014.

Read the entire report here.

And here's the figure showing all the projections (click for a larger version):

The September minimums for the last 10 years (in millions km2, found here):

    2005: 5.57
    2006: 5.92
    2007: 4.30
    2008: 4.73
    2009: 5.39
    2010: 4.93
    2011: 4.63
    2012: 3.63
    2013: 5.35
    2014: 5.28

Again, it's nice to see some people who comment here and /or on the Forum to have again submitted contributions, like Rennie, Cole, Hamilton, Dekker and of course Chris Reynolds. Chris' projection of 5.15 million km2 for the September average is right between that of Schröder's 5.1 million km2 - whose projection I discussed in this recent blog post concerning melt ponds during May- and that of Zhang's 5.2 million km2, based on the PIOMAS model. These are among the best sources of projections (melt ponds and ice thickness) in my opinion, and so Chris' projection looks well-based and solid for the time being.

The 'hiatus' and the Arctic

There's a new research paper out that will probably set the blogosphere ablaze in coming days, especially the fake skeptic part of it. Why? Because it espouses a theory that explains the slowdown in the rate of temperature rise of the past decade and a half (depending on your starting point).

According to the paper by Cowtan and Way, called Coverage bias in the HadCRUT4 temperature series and its impact on recent temperature trends, the slowdown is actually smaller, but it's not apparent because temperatures aren't recorded properly in a couple of areas around the globe, the most important being, of course, the Arctic.

This doesn't really come as a surprise, as we have seen the massive temperature spikes since 2007, especially during freeze-up when the Arctic Ocean releases all the heat accumulated during the melting season to be able to freeze up. Apparently there are a lot differences in the way these temperatures are measured or inferred by the various global temperature data sets.

You can read more about this in a blog post by Stefan Rahmstorf on RealClimate (where I took the graph on the upper right from), but I'd also like to draw attention to a blog post from last April that also looks at some discrepancies between the GISS LOTI and NCEP/NCAR data sets (Cowtan and Way focus on HadCRUT4). The analysis is done by - who else - Chris Reynolds on his Dosbat blog. Here's an excerpt and a graph:

As with the previous post on Arctic Amplification it is apparent that summer warming is negligible, this is due to energy going into melting ice, not raising temperatures. However the latent heat of energy melting ice, and ocean warming, is released in September to November, with later warming possibly due to thinner ice and ice growth.

These temperature anomalies will only be picked up by a handful of meteorological stations on islands in the Arctic, therefore will not be being strongly represented in GISS LOTI. It seems to me that rather than concluding that NCEP/NCAR is wrongly showing warming of a pattern shown by other reanalysis datasets, and backed up by mechanistic understanding of the changes in sea ice, it is more likely that GISS LOTI is missing a significant element of warming that could be as large as an extra 0.5degC in the annual average.

Read all of it here.

So it could be that the 'hiatus' in global temperature rise really isn't one. What will happen when the Sun becomes more active again, ENSO isn't dominated by La Niña, China and India start filtering aerosols out of their emissions? The prospect worries me, to be frank, as I don't think temperatures in the Arctic will drop any time soon, despite the cold summer we just witnessed.

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UPDATE

Here's a very nice graph produced by Jos Hagelaars from the Our Changing Climate blog that shows that the slowdown (or 'hiatus' or 'pause') in global atmospheric temperature increase hasn't disappeared, it has just become smaller because of Cowtan and Way's inclusion of the Arctic and other data-less regions (update: due to a calculation error the graph has been updated):

The fact that the upward trend isn't going up as fast in the period since the 70's still probably has to do with ENSO being dominated by La Niñas, an inactive Sun, Asian aerosols, etc. There's a good chance that even if all these things don't flip back and keep dampening atmospheric temps, the rate of temperature increase will gradually go back to what it was. And the Arctic will probably continue to get warmer much faster than the rest of the globe.

Commenter Dominik Lenné also has an interesting back-of-the-spreadsheet analysis on his blog showing how some of the 'missing' heat (I don't miss it at all) might have gone into melting Arctic sea ice. Rob Dekker, get over there and have a look (if you have the time): Global Warming 'hiatus': it might be the ice

The real AR5 bombshell

The whole fake skeptic propaganda effort disguised as 'leak' is boring me to death, but of course it's interesting to have a sneak peek preview of the IPCC Fifth Assessment Report (AR5) and see what they will have to say about Arctic sea ice. Geoff Beacon from the Brussels Blog already had a go at it, and found some frown inducing remarks. But for the sake of chronology I'm starting with first things first. 

From the Summary for Policymakers:

The average decadal extent of Arctic sea ice has decreased in every season since satellite observations commenced in 1979. The overall decrease in sea ice extent over the period 1979–2011 has been 3.9 [3.7 to 4.1] % per decade with larger changes occurring in summer and autumn (see Figure SPM.1). There is robust evidence of a decline in ice thickness, and in ice volume. The overall mean winter thickness has about halved between 1980 and 2009 {4.2.2}.

This, of course, is correct, and should give any sensible person pause. Given the magnitude of the event, the rate at which it is progressing (see long-term graphs), and the uncertainties with regards to possible consequences (in other words: we don't know what the worst case scenario could be), it's clear that just this short paragraph in the SMP (Summary for Policymakers) is enough to warrant some serious policymaking, which, I'm sorry to say, is not in favour of business-as-usual. Well done, IPCC!

But then, further on in the SMP, we get this:

There is very high confidence that climate models realistically simulate the annual cycle of Arctic sea ice extent, and there is high confidence that they realistically simulate the trend in Arctic sea ice extent over the past decades. {9.4.3}.

Very high confidence? I don't know about that, but before going to Chapter 9 let's first have a closer look at Chapter 4: Observations: Cryosphere, section 4.2.2.1:

Models are improving, but can they catch up?

All models are wrong, but some are useful, as the saying goes. However, when looking at how Arctic sea ice decline is modeled, one might be tempted to say that all sayings are useful, but some are wrong. To be fair, I should be the last person taking a piss at climate models. Hundreds of brilliant scientists, engineers and IT specialists are giving their best every day to make supercomputers come up with scenarios that project future changes. Unfortunately, there is no Planet B to experiment on.

But we have come to a point where fake skeptics show up in television programmes (such as last week's BBC Newsnight) and use modeled predictions for Arctic sea ice in the 2007 IPCC Fourth Assessment Report as an argument not to be worried about the disappearance of Arctic sea ice, because "none of them shows it melting before the year 2070 on a regular basis in the summer" (quote from UK Conservative MP Peter Lilley).

As always, they're not telling the whole story:

This image (taken from the Climate Crocks blog) comes from a GRL research paper by Stroeve et al. that was published in 2007, detailing how models that participated in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3) were doing compared to observations (red line). The 2011 dot was drawn in, based on NSIDC data on September 7th of last year. Commenter Tim took the liberty of drawing in the new 2012 record. This picture saves us the 1000 words needed to explain how off models are when it comes to matching observations, which essentially makes their projections worthless.

But as the Arctic sea ice cover has changed radically in just 6 years, so have new and improved models started a new round of simulations and projections for the Phase 5 project (CMIP5) for the next IPCC assessment report. And again, Dr. Julienne Stroeve and her colleagues from the NSIDC, NCAR and the Voeikov Main Geophysical Observatory in Russia, have taken a look at how these models are faring in a new GRL paper that was published three weeks ago in Geophysical research Letters: Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations.

From the introduction: