Archive for the ‘Climate change’ Category

30th Anniversary of Farman et al. (1985) – the ozone hole paper

May 15, 2015

It’s been 30 years since Farman et al. published their paper on the ozone “hole”. (Well, I’m a day early but who posts on Saturdays, eh?)

Farman_abstract

It had a huge impact: it’s been cited nearly 3,000 times and accelerated the negotiations that resulted in the Montreal Protocol, which helped phase out the chemicals that were damaging the ozone layer. Those chemicals can stay in the atmosphere for a very long time so the ozone “hole” is far from fixed, which can sometimes cause confusion over the effectiveness of the Montreal Protocol. It’ll probably be decades still until the “hole” is fixed (see the Annual Records at the bottom left-hand side of this NASA page for historical data.)

This slow recover particularly interests me at the moment as I recently did a little bit of work on the health risks associated with the hole at its peak for those living and working in Antarctica. This may become a more important problem in the future if further warming and ice sheet retreat make regions like the Antarctic Peninsula easier to inhabit, work in and/or exploit. Hopefully I’ll get to a bit more work on this soon.

And I’ve always had a real soft spot for the paper as the ozone “hole” was the first time that I remember being aware of an environmental issue, despite being pretty young at the time (I was at primary school 30 years ago). I suspect that it played a large in shaping my view of the world and my career direction so I thought I should note the anniversary.

So, Happy Birthday Farman et al. (1985)!

If you want to get deeper into the ozone “hole” then Chapter 7 in Volume I of “Late Lessons from Early Warnings”, written by Joe Farman, is quite nice and the chapter in Merchants of Doubt is a good read on this as well. [Update, 15/5/2015 0937] There also a BBC “Costing the Earth” episode on the 30th anniversary of the ozone hole but I’ve not listened to it yet (thanks to @jimmcquaid on twitter for pointing me in that direction).

Reference

Farman, J., Gardiner, B., & Shanklin, J. (1985). Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction Nature, 315 (6016), 207-210 DOI: 10.1038/315207a0

Health risks on the Antarctic Peninsula – what’s happening with the ozone hole, UV exposure, environmental change and funding for Antarctic science?

April 3, 2015

ResearchBlogging.org

I recently had a paper published in Antarctic Science – I don’t think that it’ll set the world on fire but it was quite interesting in how it came about so I thought I’d write a blogpost about it.

The study

The measurements for the study were taken by a team who sailed across the Drake Passage and then then spent some time on and around the Antarctic Peninsula. They deployed a small “badge” each day that responds to sunlight in a way that allows you to subsequently work out how much UV radiation they were exposed to. From these measurements we concluded that the UV exposure experienced was comparable to temperate, mid-latitude locations in the spring/late summer. Obviously the team was very well covered as it’s cold down there but this can nonetheless have impacts on the eyes and exposed skin.

This is quite important as the ozone “hole” over Antarctica is likely to be about as bad as it will get before recovering over the next few decades and exposure risk might increase in this region if there are significant environmental changes (e.g. further warming, ice sheet retreat). This paper represents something of a pilot study so I’d love to get a more rigorous experiment up-and-running one day.

The BSAE team on the Antarctic Peninsula. The badges were mounted on one of the sledges. Photo taken by Martin Densham.

The BSAE team on the Antarctic Peninsula. The badges were mounted on one of the sledges. Photo taken by Martin Densham.

The study’s origins: networking on social media

The idea for the experiment and the paper first came about on twitter. Someone I’d never previously worked with (or met) invited me along to a planning meeting for the 2012 British Services Antarctic Expedition (BSAE) simply because I had a twitter account where I posted interesting stories about Antarctica.

I then cobbled together a tiny bit of money from the Royal Meteorological Society and the Royal Geographical Society (with the Institute of British Geographers) to get the badges produced and analysed at the University of Manchester.

I was quite impressed that we managed to get a relatively interesting bit of work done with so little resource. Which brings us on to…

…funding for Antarctic science

Budgets for science have not been increasing recently so perhaps it’s time that we have to start thinking of less traditional ways of getting work done. My example might not be particularly useful as it all happened largely by accident! However, there’s an interesting piece in The Conversation by Adrian McCallum about the role of private funding in Antarctic research that is probably more informed on this topic. Might be worth a read if you’re thinking of this type of thing.

Reference

Russell, A., Gohlan, M., Smedley, A., & Densham, M. (2014). The ultraviolet radiation environment during an expedition across the Drake Passage and on the Antarctic Peninsula Antarctic Science DOI: 10.1017/S0954102014000790

News Year’s Honours: Eric Pickles still sucks; and well done Tim Palmer!

December 31, 2014

I just had a quick look through the New Year’s Honours list and was surprised and happy to see quite a few (6 or 7) people with a link to flood management, including a few from the Environment Agency.

I thought that this was significant as it wasn’t that long ago that Eric Pickles (the Communities Secretary) was questioning the EA’s expertise, which was stupid. And it seems that the UK Honours Committee doesn’t agree with him either. So good on them.

Also good news that Tim Palmer (Professor in Climate Physics at Oxford) got recognised too (OBE). I love Tim’s papers and it was his work that largely inspired me to go into climate research.

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?


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