Archive for the ‘Climate change’ Category

Is the public debate on climate change turning a corner?

September 23, 2014

When I started this blog in late 2009, things were not good with climate change in the media: the UEA/climategate emails had just been leaked and COP15 in Copenhagen didn’t go so well.

A couple of years before that, though, I felt that there was quite a lot of optimism. IPCC AR4 and the Stern Review had made a real splash. It felt like there could be some significant, global action on climate change. But that didn’t happen.

However, maybe we’ve turned a corner in the last week or so.

The obvious focal point is the really successful People’s Climate March, which took place at many locations around the world and attracted far more people than were estimated in advance. I went along to the London one and there was a good atmosphere and loads of people, somewhere between 20,000 and 40,000 according to different estimates. I think the prediction beforehand was for around 10,000 people turning out.

400,000 at the climate march in New York

400,000 at the climate march in New York

But that’s not the only positive news.

The Rockerfeller family have decided to withdraw their investments in fossil fuels. The Guardian describe this as a big “symbolic boost” for the fossil fuel divestment movement in general. I suppose I should investigate our investments at Brunel University and see if we can do anything on this front as well.

And Google’s chairman, Eric Schmidt, has used some strong words in announcing their decision to leave the American Legislative Exchange Council lobby group, who also work to stifle progress on positive climate change responses. The choice quote from Schmidt being:

The facts of climate change are not in question anymore. Everyone understands climate change is occurring, and the people who oppose it are really hurting our children and our grandchildren and making the world a much worse place. And so we should not be aligned with such people — they’re just, they’re just literally lying.

So hopefully this means that there’ll be lots of people watching the UN Climate Summit today and expecting something positive.

I won’t be holding my breath but I’m feeling more confident than I have done for a few years.

Thunderstorms in the IPCC AR5

January 28, 2014

It’s been a while since I blogged; I hope you didn’t think I’d forgotten you! My workload has “shifted” recently and I’m doing a bit more teaching/supervision/management these days. Blogging has taken a bit of a backseat. So I’m a bit late on this one but thought that it was still interesting. Anyway, enough of the excuses…

I’ve often thought it was odd that the potential changes in frequency and/or intensity of small scale severe storms/thunderstorms – one of my areas of research – was absent from the IPCC TAR, AR4 and SREX.

This has been put right in the IPCC AR5, which was published in late 2013 but, if anything, it highlights some of the problems with the slow and rigidly structured IPCC process.

So here’re a few sentences from IPCC AR5 that deal with severe thunderstorms:

The large-scale environments in which [severe thunderstorms] occur are characterized by large Convective Available Potential Energy (CAPE) and deep tropospheric wind shear (Brooks et al., 2003; Brooks, 2009). Del Genio et al. (2007), Trapp et al. (2007; 2009), and Van Klooster and Roebber (2009) found a general increase in the energy and decrease in the shear terms from the late 20th century to the late 21st century over the United States using a variety of regional model simulations embedded in global-model SRES scenario simulations. The relative change between these two competing factors would tend to favour more environments that would support severe thunderstorms, providing storms are initiated.

Overall, for all parts of the world studied, the results are suggestive of a trend toward environments favouring more severe thunderstorms, but the small number of analyses precludes any likelihood estimate of this change.

It’s a pretty good, concise summary of work in this area up to 2012/13. (I’ve not included some of the text on examples and the few studies outside of the US, you can find the full text here towards the end of section 12.4.5.5 Extreme Events in the Water Cycle. There’s another bit in 2.6.2.4 Severe Local Weather Events as well.)

However, whilst the IPCC report was being published, this paper came out:

Diffenbaugh, N. S., Scherer, M. and Trapp, R. J. (in press) “Robust increases in severe thunderstorm environments in response to greenhouse forcing” PNAS, doi: 10.1073/pnas.1307758110

They say:

We use an ensemble of global climate model experiments to probe the severe thunderstorm response. We find that this ensemble exhibits robust increases in the occurrence of severe thunderstorm environments over the eastern United States. In addition, the simulated changes in the atmospheric environment indicate an increase in the number of days supportive of the spectrum of convective hazards, with the suggestion of a possible increase in the number of days supportive of tornadic storms.

It’s a much more up-to-date and robust analysis of the problem and even uses the CMIP5 climate projections that form the backbone of the IPCC AR5. (I’ve been working on something similar for the Northern Hemisphere but not quite finished it yet!) I guess that this paper must have been accepted for publication after the deadline for the IPCC process so it isn’t mentioned. It’s a shame as a citation to this paper would have added something to the argument.

And this seems to be a problem with the IPCC. Climate science research is a much bigger area now than when the IPCC process started in the late 1980s/early 1990s. So a whole area of research (e.g. severe thunderstorms in a changing climate) becomes a couple of sentences with the most up-to-date paper missing.

As good as the IPCC has been over the years, perhaps it’s time to move on. The SREX example seems to be a good one: a multi-disciplinary, timely analysis of an important area. I think that a series of special reports like SREX would be a better use of valuable time than an AR6.

Tornadoes and climate change

May 21, 2013

I’m sure you’ve already seen the sad news about the tornado in Oklahoma – it looks like it has done a lot of damage and claimed a lot of lives.

Tornadoes are not uncommon in that area and it is almost impossible to make good forecasts of where they will hit as they are too small for computer forecast models to capture. Even the scientific understanding of how they form is not great as it’s really hard to get good measurements of them in their destructive phase.

I’m sure that the discussion will now turn to the role of climate change in this particular event but, as usual, that’s a very difficult question to ask despite recent efforts on this front. At one level it’s quite easy to speculate that if the warm air heading north from the Gulf of Mexico that fed the storm that spawned the tornado was warmer than it otherwise would have been then, yes: climate change could have made this event more likely and/or stronger.

But the atmosphere doesn’t really work like that and the number of complex factors required to produce any specific tornado makes the cause and effect arguments that are wrapped up in the  “link to climate change” question very, very difficult.

But perhaps we think about this more statistically and ask whether tornadoes will get stronger and/or more likely in a warmer future climate.

Again, this is really difficult because climate models certainly don’t have the power (i.e. high enough resolution) to represent tornadoes. So you can’t just go through climate model data and count the tornadoes that it thinks will occur.

If we think statistically again, though, we can look for the change in larger scale conditions that usually produce tornadoes.

Unfortunately, this isn’t particularly clear either.

Whilst the increased warmth and moisture predicted by climate models will mean more energy would be available to developing tornadoes, the climate projections also show a decrease in the occurrence of the wind patterns that are needed to form tornadoes.

Nonetheless, one thing that does seem likely is that we can still reduce the likelihood of a stormier future world. If you compare the storminess of climate simulations with, say, “medium” and “high” greenhouse gas concentrations (as done here) then the “medium” case looks better than the “high”.

More on Antarctic sea ice

April 11, 2013

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

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.)

April 1, 2013

Quick_fix

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

March 31, 2013

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 in Arctic and Antarctic

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)

November 8, 2012

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?

Papers based on CMIP5 data

March 14, 2012

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

Seth et al. (2013) “CMIP5 Projected Changes in the Annual Cycle of Precipitation in Monsoon Regions”  Journal of Climate 2013, doi: http://dx.doi.org/10.1175/JCLI-D-12-00726.1

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

Journal of Climate Special Collection on C4MIP

Books

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

Michael Mann on TEDx – the scientization of politics

December 7, 2011

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.


Follow

Get every new post delivered to your Inbox.

Join 2,586 other followers