More on Antarctic sea ice

I wrote a post recently on Antarctic sea ice where I only included sea ice extent at minimum month, mostly because it was a nice figure.

Anyway, I just noticed this nicer figure from a new paper in the International Journal of Climatology (Tareghian and Rasmussen, 2013):

Quantile regressions (20th, 50th, and 80th percentiles) and standard linear regression of monthly sea ice extent (1979–2010) for (a) the Northern Hemisphere and (b) the Southern Hemisphere from Tareghian and Rasmussen (2013)

This shows the difference in the annual trends as well as the seasonal ones.

Reference

Tareghian, R. and Rasmussen, P. (2013), Analysis of Arctic and Antarctic sea ice extent using quantile regression. Int. J. Climatol., 33: 1079–1086.

Climate quick fix! (But please sign this disclaimer first.)

Geoengineering sometimes looks like a good option: international agreements on greenhouse gas emission reductions don’t seem to be going anywhere so having a back-up plan to deal with global temperatures would be useful.

However, there are potentially big problems with tinkering with the climate system more than we already have.

Haywood et al. outline one of these problems in a new Nature Climate Change paper that was published this week.

They look at the response of the climate in models when you add aerosol particles to the stratosphere – this will reduce the amount of energy entering the climate system by reflecting some of it away.

The unintended consequences, however, are not good: global rainfall patterns change as a result of the intervention and could lead to droughts in some areas e.g. the Sahel. (These outcomes are sensitive to where the aerosol is added and, of course, are subject to all the usual model uncertainties.)

So it would seem that geoengineering might only be useful if there are international agreements on who takes responsibility for the outcomes. Best get those negotiations started ASAP then!

There’s some more comment in The Gaurdian.

Antarctic sea-ice growth in Nature Geoscience

There’s a new paper on Antarctic sea-ice in Nature Geoscience so I thought it might be a good time to have a quick look at how this story has developed recently. (The short version: the small increase in Antarctic sea ice is most likely a result of a complicated coruination of: density changes in the surface layer of the Southern Ocean (a result of temperature and salinity changes), which stops warm deep water reaching the surface and melting the sea ice; changing wind patterns (partially a result of ozone depletion) that leads to ice drift increase and increased sea ice extent; and melting from the bottom of ice shelves adding cool water to the ocean surface layer that further reduces deeper warm water reaching the surface and reducing sea ice melt.)

Firstly, though, why does anyone care about Antarctic sea-ice? Well, it’s been increasing a little recently. This isn’t quite what you’d expect in a changing climate where the change is being driven by an increase in energy being retained in the system by an increase in greenhouse gases in the atmosphere.

In contrast, we often hear about sea-ice loss in the Arctic, which is often linked with climate change. However, if we compare the Arctic loss with the Antarctic gain you can see that one is clearly more of an issue than the other:

Sea ice extent for the month when its at its minimum (i.e. the end of local summer) Source: James Hansen

Nonetheless, its still interesting to think about why Antarctic sea ice is increasing.

The best theory around five years ago (Zhang 2007) was that the surface layer of the Southern Ocean was changing density and that this stops the warmer water below getting to the surface and melting the sea ice. The change in density itself is driven by a couple of factors, such as increased evaporation from warmer Southern waters that increases rainfall in the seas around Antarctica and freshens the water and changes in salinity driven by the sea ice changes themselves (sea ice rejects salt as it forms).

Last year, the big advance was the use of satellite observations to show that changing wind patterns in the Southern Hemisphere (which I’ve written about here) were driving the sea ice extent increase via increased ice drift (Holland and Kwok 2012).

The new paper (Bintanja et al. 2013) shows that melting from the bottom of ice shelves – where the Antarctic glaciers flow out over the ocean – produces a layer of cold water that stops warmer water below reaching the surface and slowing sea-ice growth. Although,  Holland (of Holland and Kwok) isn’t convinced that the experiments are a good demonstration of the mechanism.

So this is quite a complicated situation to understand. However, the ocean and air temperatures around Antarctica aren’t decreasing so that isn’t the reason for the sea ice increase, even though it may seem like the most obvious. To find out the real reason you need to dig a little deeper.

Communicating Climate Science (but don’t mention the b-word)

Blog.

There, I said it.

Which, as far as I can remember, is more than it was mentioned in the 7 talks or during the panel discussion at yesterday’s RMetS meeting on Communicating Climate Science.

Just to re-iterate, in a 3 hour meeting about Communicating Climate Science I don’t remember anyone saying the word “blog”.

Also to be clear, I thought the meeting was really interesting and well worth going to to. But, looking back on the event, I’m amazed that I don’t think anyone mentioned the impact of blogging on climate science communication, how it could be used better by the community or even that it exists.

Which is odd because two of the speakers are very good bloggers (Alice Bell and Adam Corner) and I noticed a few in the audience (e.g. Tamsin Edwards and Bob Ward, who seems like a blogger without a blog, unless I’ve missed it!)

So, did anyone else notice this or did I just nod off at the wrong moment?

Stormy weather ahead? at @ScienceLondon SciBar

I gave a little talk last night at the SciBar in London. It was a lot of fun and hope people enjoyed it! I’d recommend that you go along to one of their future events.

So I was talking about some of my current research on future storminess. This was kind of based on a post I wrote for the Nature Soapbox Science blog a few months ago (and then re-posted here).

One of the issues with looking at convective storms, or thunderstorms, in computer climate models is the resolution of the model i.e. the size of the boxes that the model splits the atmosphere up into. Ideally you’d have very small boxes so that you can “build” the storms in the model. But that isn’t possible given current computing power.

To demonstrate the importance of this at the SciBar I brought along some lego, duplo and a cube and asked people to make the best storm they could (see picture). I hope that this worked!

How different models might see a thunderstorm, like the one in the picture at the top. So, from left to right, the lego model is how a quite high resolution weather model would see the cloud, the duplo cloud in the middle is how a low resolution weather model would build the cloud and, on the right, is how a climate model would see the cloud i.e. it doesn’t. Just to clarify, the butterfly and pig would not be included in the climate model

What do other people think about this method of explaining the effect of model resolution? I guess someone’s used it before but I quite liked it all the same.

(By the way, sorry I didn’t have any results to show at the talk! Keep an eye out here and I’ll post something when it’s ready to roll.)

Papers based on CMIP5 data

I happened to ask over on Ed Hawkin’s blog whether he knew of any list of publications based on CMIP5 data (i.e. the suite of climate projections being produced for the IPCC AR5). He pointed me to the PCMDI page, which at the time was blank. So, here is my list of papers based on CMIP5 that I’ll try and keep up to date:

UPDATE: There are now papers being added to the official PCMDI list. It seems as though anyone can add papers to that list so there are lots of “Submitted” papers. The list below is of papers that have been published.

Individual papers

Ahlström et al (2012) “Robustness and uncertainty in terrestrial ecosystem carbon response to CMIP5 climate change projections” Environ. Res. Lett., 7, 044008.

Andrews et al. (2012) “Forcing, Feedbacks and Climate Sensitivity in CMIP5 Coupled Atmosphere-Ocean Climate Models” Geophys. Res. Lett., doi:10.1029/2012GL051607

Arora et al. (2011) “Carbon emission limits required to satisfy future representative concentration pathways of greenhouse gases” Geophys. Res. Lett., 38, L05805.

Biasutti (2013) “Forced Sahel rainfall trends in the CMIP5 archive” J. Geophys. Res., DOI: 10.1002/jgrd.50206, in press.

Bellouin et al. (2011) “Aerosol forcing in the Climate Model Intercomparison Project (CMIP5) simulations by HadGEM2-ES and the role of ammonium nitrate” J. Geophys. Res., 116, D20206.

Branstator and Teng (2012) “Potential Impact of Initialization on Decadal Predictions as Assessed for CMIP5″ Geophys. Res. Lett., doi:10.1029/2012GL051974, in press.

Cai et al. (2012) “More extreme swings of the South Pacific convergence zone due to greenhouse warming” Nature, 488, 365–369.

Chang et al (2012) “CMIP5 multi-model ensemble projection of storm track change under global warming” J. Geophys. Res., doi:10.1029/2012JD018578, in press.

Christensen and Boberg (2012) “Temperature dependent climate projection deficiencies in CMIP5 models” Geophys. Res. Lett., 39, doi:10.1029/2012GL053650, in press.

Dai et al. (2012) “Increasing drought under global warming in observations and models” Nature Clim. Change, doi:10.1038/nclimate1633.

Dobrynin et al. (2012) “Evolution of the global wind wave climate in CMIP5 experiments” Geophys. Res. Lett., doi:10.1029/2012GL052843, in press.

Driscoll et al. (2012) “Coupled Model Intercomparison Project 5 (CMIP5) simulations of climate following volcanic eruptions”  J. Geophys. Res., doi:10.1029/2012JD017607, in press.

Dunn-Sigouin and Son (2013) “Northern Hemisphere blocking frequency and duration in the CMIP5 models” J. Geophys. Res., DOI: 10.1002/jgrd.50143, in press.

Gillett and Fyfe (2013) “Annular mode changes in the CMIP5 simulations” Geophys. Res. Lett., DOI: 10.1002/grl.50249, in press.

Good et al. (2011) “A step-response simple climate model to reconstruct and interpret AOGCM projections” Geophys. Res. Lett., 38, L01703.

Guilyardi et al. (2012) “A first look at ENSO in CMIP5″ CLIVAR Exchanges, 17, 29-32.

Haywood et al. (2011) “The roles of aerosol, water vapor and cloud in future global dimming/brightening” J. Geophys. Res., 116, D20203.

Heuzé et al. (2013) “Southern Ocean bottom water characteristics in CMIP5 models” Geophys. Res. Lett., DOI: 10.1002/grl.50287.

Jiang et al. (2012) “Evaluation of Cloud and Water Vapor Simulations in CMIP5 Climate Models Using NASA “A-Train” Satellite Observations” J. Geophys. Res., doi:10.1029/2011JD017237. GFDL summary.

Jones et al. (2011) “The HadGEM2-ES implementation of CMIP5 centennial simulations” Geosci. Model Dev., 4, 543–570.

Kamae and Watanabe (2012) “On the robustness of tropospheric adjustment in CMIP5 models” Geophys. Res. Lett., doi:10.1029/2012GL054275, in press.

Kawase et al. (2011) “Future changes in tropospheric ozone under Representative Concentration Pathways (RCPs)” Geophys. Res. Lett., 38, L05801.

Kelley et al. (2012) “Mediterranean precipitation climatology, seasonal cycle, and trend as simulated by CMIP5″ Geophys. Res. Lett., doi:10.1029/2012GL053416, in press.

Kim and Yu (2012) “The Two Types of ENSO in CMIP5 Models” Geophys. Res. Lett., doi:10.1029/2012GL052006. [paper pdf here]

Kim et al. (2012) “Evaluation of short-term climate change prediction in multi-model CMIP5 decadal hindcasts” Geophys. Res. Lett., doi:10.1029/2012GL051644.

Knutti and Sedlácek (2012) “Robustness and uncertainties in the new CMIP5 climate model projections” Nature Climate Change, doi:10.1038/nclimate1716, in press.

Knutti et al. (2013) “Climate model genealogy: Generation CMIP5 and how we got there” Geophys. Res. Lett., 40, doi:10.1002/grl.50256.

Kug et al. (2012) “Improved simulation of two types of El Niño in CMIP5 models” Environ. Res. Lett., 7, 034002, doi:10.1088/1748-9326/7/3/034002.

Lau et al. (2013) “A canonical response of precipitation characteristics to Global Warming from CMIP5 models” Geophys. Res. Lett., DOI: 10.1002/grl.50420

Liu et al. (2012) “Co-variation of temperature and precipitation in CMIP5 models and satellite observations” Geophys. Res. Lett., doi:10.1029/2012GL052093, in press.

Massonnet et al. (2012) “Constraining projections of summer Arctic sea ice” The Cryosphere Discuss., 6, 2931-2959.

Meijers et al. (2012) “Representation of the Antarctic Circumpolar Current in the CMIP5 climate models and future changes under warming scenarios” J. Geophys. Res., doi:10.1029/2012JC008412, in press.

Mizuta (2012) “Intensification of extratropical cyclones associated with the polar jet change in the CMIP5 global warming projections” Geophys. Res. Lett., doi:10.1029/2012GL053032, in press.

Monerie et al. (2012) “Expected future changes in the African monsoon between 2030 and 2070 using some CMIP3 and CMIP5 models under a medium-low RCP scenario” J. Geophys. Res., doi:10.1029/2012JD017510, in press.

Nam et al. (2012) “The ‘too few, too bright’ tropical low-cloud problem in CMIP5 models” Geophys. Res. Lett., doi:10.1029/2012GL053421, in press.

Oleson (2012) “Contrasts between Urban and Rural Climate in CCSM4 CMIP5 Climate Change Scenarios” J. Climate, 25, 1390–1412.

Osprey et al. (2013) “Stratospheric Variability in Twentieth-Century CMIP5 Simulations of the Met Office Climate Model: High Top versus Low Top” J. Climate, 26, 1595–1606.

Reichler et al. (2012) “A stratospheric connection to Atlantic climate variability” Nature Geoscience, doi:10.1038/ngeo1586.

Rotstayn et al. (2012) “Aerosol- and greenhouse gas-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations” Atmos. Chem. Phys., 12, 6377-6404.

Sabeerali et al. (2013) “Simulation of boreal summer intraseasonal oscillations in the latest CMIP5 coupled GCMs” J. Geophys. Res., doi: : 10.1002/jgrd.50403, in press.

Sarojini et al. (2012) “Fingerprints of changes in annual and seasonal precipitation from CMIP5 models over land and ocean” Geophys. Res. Lett., doi:10.1029/2012GL053373, in press.

Seager et al. (2012) “Projections of declining surface-water availability for the southwestern United States” Nature Climate Change, doi:10.1038/nclimate1787

Sillmann et al. (2013) “Climate extremes indices in the CMIP5 multi-model ensemble. Part 1: Model evaluation in the present climate” J. Geophys. Res., doi: 10.1002/jgrd.50203, in press.

Stevenson et al. (2012) “Will There Be a Significant Change to El Niño in the Twenty-First Century?” J. Climate, 25, 2129–2145.

Stroeve et al. (2012) “Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations” Geophys. Res. Lett., 39, L16502, doi:10.1029/2012GL052676.

Su et al. (2012) “Diagnosis of regime-dependent cloud simulation errors in CMIP5 models using “A-Train” satellite observations and reanalysis data” J. Geophys. Res., doi:10.1029/2012JD018575, in press.

Taylor et al. (2011) “An Overview of CMIP5 and the Experiment Design” Bull. Am. Meteorol. Soc.

Tian et al. (2013) “Evaluating CMIP5 Models using AIRS Tropospheric Air Temperature and Specific Humidity Climatology” J. Geophys. Res., 118, in press.

Todd-Brown et al. (2012) “Causes of variation in soil carbon predictions from CMIP5 Earth system models and comparison with observations, Biogeosciences Discuss., 9, 14437-14473.

Turner et al. (2013) “An Initial Assessment of Antarctic Sea Ice Extent in the CMIP5 Models” J. Climate, 26, 1473–1484.

Villarini and Vecchi (2012) “Twenty-first-century projections of North Atlantic tropical storms from CMIP5 models” Nature Climate Change, doi:10.1038/nclimate1530.

Villarini and Vecchi (2013) “Projected Increases in North Atlantic Tropical Cyclone Intensity from CMIP5 Models” J. Climate, 26, 3231–3240.

Wang  and Overland (2012) “A sea ice free summer Arctic within 30 years-an update from CMIP5 models” Geophys. Res. Lett., doi:10.1029/2012GL052868, in press.

Watanabe et al. (2011) “MIROC-ESM 2010: model description and basic results of CMIP5-20c3m experiments” Geosci. Model Dev., 4, 845-872.

Williams et al (2012) “Diagnosing atmosphere–land feedbacks in CMIP5 climate models” Environ. Res. Lett., 7, 044003

Xu and Powell Jr. (2012) “Intercomparison of temperature trends in IPCC CMIP5 simulations with observations, reanalyses and CMIP3 models” Geosci. Model Dev. Discuss., 5, 3621-3645

Yang and Christensen (2012) “Arctic sea ice reduction and European cold winters in CMIP5 climate change experiments” Geophys. Res. Lett., doi:10.1029/2012GL053338, in press.

Yeh et al. (2012) “Changes in the Tropical Pacific SST Trend from CMIP3 to CMIP5 and Its Implication of ENSO” J. Climate, 25, 7764–7771.

Yin (2012) “Century to multi-century sea level rise projections from CMIP5 models” Geophys. Res. Lett., doi:10.1029/2012GL052947, in press.

Ying and Chong-Hai (2012) “Preliminary Assessment of Simulations of Climate Changes over China by CMIP5 Multi-Models” Atmospheric and Oceanic Science Letters, in press.

Zhang and Jin (2012) “Improvements in the CMIP5 simulations of ENSO-SSTA meridional width” Geophys. Res. Lett., doi:10.1029/2012GL053588, in press.

Zunz et al. (2012) “How does internal variability influence the ability of CMIP5 models to reproduce the recent trend in Southern Ocean sea ice extent?” The Cryosphere Discuss., 6, 3539-3573.

Special Issues/Collections (some of the above papers may be in these Special Issues)

Climatic Change special issue on the Representative Concentration Pathways

Climate Dynamics IPSL and CNRM CMIP5 Special Issue (mostly submitted papers as of 15/03/2012)

Geoscientific Model Development Special Issue on Community software to support the delivery of CMIP5 (no papers linked to it as of 15/03/2012)

Journal of Climate Special Collection on CCSM4 and CESM1

Books

Dong et al. (2012) The Atlas of Climate Change — Based on SEAP-CMIP5. Springer. 200pp.

Michael Mann on TEDx – the scientization of politics

Michael Mann (of “hockey stick” fame) has just has a TEDx talk published.

It’s bookended by the things you’d expect – a quick run through of climate science and potential solutions – but the bits in the middle are probably the most interesting.

Climate science is often accused of becoming too politicised (usually because of the role of the  IPCC) but Mann’s argument here is that it happened the other way round: that politics became “scientized” in order to cast doubt over the scientific findings that do not align with paticular political views. At one point he refers to Merchants of Doubt, a book which presents evidence from the last 50 years covering a number of scientific topics that have caused problems for certain industries, and Mann’s case seems to add to those stories.

Weather and climate evening at the Manchester Science Festival

It’s the Manchester Science Festival this week and as part of it there’s a Weather and Climate evening on Thursday. It starts with a live recording of the Barometer podcast, which I sometimes (well, not very often) contribute to. Anyway, sounds like they’ve got some fun stuff planned and they’ll be plenty of time for Q&A.

More BEST (but still not peer reviewed)

The BEST story rumbles on but still no peer reviewed results.

Instead, they’ve made 4 manuscripts available that have been submitted on their methods, the influence of the urban heat island, temperature records and stations quality for the US and global temperature variations (all 4 links go to pdfs).

This seems to be the key figure:

"Comparison of the Berkeley Average to existing land-only averages reported by the three major temperature groups." The differences in the late 20th Century arise from different definitions of "land" used by the four groups - the paper says that global averages match better in this period but I couldn't see that figure in the papers - if it's not there, it'd be nice to add it.

Here are a few interesting quotes from the papers after a very quick read. From the first paper:

This change [in global land mean temperature] is consistent with global land-surface warming results previously reported, but with reduced uncertainty.

I’d read this as GISS, NOAA and HadCRU being pretty much on the money but they’ve found the same thing using more data (the BEST record goes back to 1800, which is nice) and a different method.

From the second paper:

The small size, and its negative sign, [of the urban heat island effect] supports the key conclusion of prior groups that urban warming does not unduly bias estimates of recent global temperature change.

This pretty much confirms the recent work of Menne et al. (2010) and the Watts paper and will hopefully put this issue to bed. Indeed, the third paper, which specifically mentions Watts in the abstract in relation to SurfaceStations, then goes on to show that US station quality makes little impact on the recorded trend.

Paper four looks at the role of ENSO and the AMO in controlling decadal variability in the temperature data. This looks like the most interesting paper to me so I’ll have a closer look at that soon.

Overall, though, there doesn’t quite seem like enough material for 4 papers here. Maybe they’re trying to make it look like they’ve done more than re-re-re-confirm the results of other groups.

John Mitchell and Simon Singh at the RMetS AGM

I went along to the Royal Meteorological Society‘s AGM yesterday. I realise this sounds pretty dull but they have a couple of talks before the AGM proper, which were very interesting. (I’m also ashamed to admit that I left the meeting before they got down to the AGM business as I was giving a talk in Guildford that evening.)

The meeting was held at the Bank of England Museum and Mervyn King, who is apparently a bit of a weather geek, gave a short introduction looking at the links between the Bank and meteorology. I thought the most interesting story was on the historical importance of wind to Bank – available credit would have to be increased when easterlies prevailed as ships could sail up the Thames and then decreased again as westerlies returned. Naturally, he also mentioned climatic impacts on the economy.

The first proper talk was by Prof. John Mitchell from the Met Office. He was being awarded the society’s Symons Gold Medal (congratulations John!) so his talk was a celebration of that.

His presentation – “What we know and what we don’t know about global warming” – was based around a series of basic questions, similar to the style of Skeptical Science. He covered topics like: Is CO2 increasing? Is the increase down to humans? Does CO2 affect climate? Is the climate changing? Why is the climate changing? What might future changes look like? Are global temperatures changing as models showed? All interesting stuff, particularly the last point where John showed some updated work from a 2000 paper by Myles Allen where the observed 2009 global temperature was in the middle of the range projected in 1996.

The point that really caught my eye, though, was on recent temperature changes. I think it was some work by Peter Stott that John was showing on the difference between 50 and 10 year temperature trend distributions in model runs forced by natural factors and a 0.2K/decade forcing (I could be wrong about this last point, I can’t remember the setups and didn’t jot them down). Anyway, whilst the 50 year trend distributions where almost completely distinct for the two types of run, the 10 year trend distributions had a considerable overlap, which is pretty interesting given what global temperatures have been doing over the last 10 years or so and what that says about global warming (i.e. possibly nothing you wouldn’t expect from a climate being forced in the way Earth’s climate is being forced).

The second speaker was Simon Singh, who spoke about Science and the Media.

There was a little time spent on climate change; Simon showed a brief email exchange he had with Martin Durkin after the broadcast of the Great Global Warming Swindle in 2007. It seems that Martin’s responses to polite criticism are as sophisticated as his documentaries. Indeed, the presentation of Martin’s emails could also be the first time that c**k and f**k have been used at a RMetS AGM. This, I think, is progress.

There was also an interesting question for Simon about the similarities between the “hide the decline” episode and an edit Simon showed us that he had made to one of his own documentaries (substituting “primes” with “numbers” in an interview with a mathematician to make it understandable for a wider audience). Simon argued that they were quite different situations as the removal of unreliable proxy data was done for scientific reasons whereas his edit was done for communication reasons. I wonder if there isn’t more of an overlap, though. I’m not sure we’ve properly acknowledged the needs of different audiences and how scientists decide to summarise their work for them.