Posts Tagged ‘Global warming’

A little bit more on BEST and Watts

March 31, 2011

I wrote a short post recently about the hot air surrounding the new surface temperature record being compiled at Berkeley.

One of the issues was the data sample that was used in preliminary BEST analysis that was being discussed.

UPDATE (31/3/2011 11:58am): Carbon Brief have some graphs to show how similar the 2% sample is to NOAA, GISS and HadCRU.

It seems that Watts was mistaken about the 2% sample of BEST data being from Japan. He updated his post in the last few days:

“ERRATA: I made a mistake regarding the 2% figure, I misheard what was being presented during my visit with the BEST team at Berkeley. As many of you may know I’m about 80% hearing impaired and the presentation made to me was entirely verbal with some printed graphs. Based on the confidentiality I agreed to, I did not get to come back with any of those graphs, notes, or data so I had to rely on what I heard. I simply misheard and thought the 2% were the Japan station analysis graphs that they showed me.

I was in touch with Dr. Richard Muller on 3/28/2011 who graciously pointed out my misinterpretation. I regret the error, and thus issue this correction about the 2% figure being truly a random sample, and not just stations in the Japan test presentation shown to me.”

It’s just a shame that he didn’t notice the contradiction between the BEST statement (“random”) and his own understanding (“Japan”) before writing his post and shouting down commenters asking for clarification (i.e. “Ah I see you are immediately back to wasting everyone’s time…“).

Why has this winter been so cold in Europe?

January 6, 2011

This post was chosen as an Editor's Selection for ResearchBlogging.orgI’ve written a couple of posts recently looking at the cold UK weather in context and how snow forms.

What I haven’t done, though, is looked at why it’s been so cold over Europe this winter (as well as last year’s winter).

It just so happens that a paper came out in the Journal of Geophysical Research recently (Petoukhov and Semenov, 2010) that might hold the answer.

They looked at whether changing the sea ice concentration in a particular area of the Arctic (the  Barents-Kara sea) in a long run of a climate model changed the conditions over Europe.

Their reason for doing this was that the very cold winter of 2005/06 was accompanied by very low sea ice in this region – they don’t mention 2009/10 and 2010/11 at all, though, as they would have been writing the paper before these cold European winters occurred.

To isolate the effect of the sea ice in this one region they use a mean state (a “climatology”) for most of the planet in the model but change the amount of ice on the  Barents-Kara sea. The results are quite surprising.

The winter wind patterns over Europe change dramatically when they changed the ice concentration from 80-100% to 40-80%. You can see this in the figure below, which is from the paper but I’ve highlighted the key areas on the wind plot and removed some of the panels.

Mean surface air temperature and 850 hPa wind anomalies for February from the model runs using 2 ice scenarios.

(When they set the sea ice close to 0%, Europe goes into a different state that is similar in temperature to the 80-100% case.)

So why does Europe get cold in a model world where the Barents-Kara sea has 40-80% sea ice concentration? In this model run, the result of this level of sea ice is to set up a big anti-cyclonic (high-pressure) anomaly over the pole. In the northern hemisphere air rotates clockwise around a high so this explains the switch in wind direction that drives the change over Europe. However, the hypothesis they present as to why the sea ice change leads to a high pressure anomaly over the pole is not straightforward and probably deserves a bit more study.

So, in essence, this all seems to be saying that it’s climate change that has led to our very cold winter! I can imagine some people finding that hard to swallow but here’s a quote from the paper that sums it up better than I just have:

Our results imply that several recent severe winters do not conflict the global warming picture but rather supplement it, being in qualitative agreement with the simulated large-scale atmospheric circulation realignment.

Anyway, all interesting stuff and I look forward to seeing some more analysis, especially a better climatology of winter temperatures in Europe and Arctic sea ice to see if that fits in with this hypothesis and a better physical model for the different changes linked with different sea ice concentrations.

UPDATE (10th Jan 2011): I just read someone claiming to have “debunked” this paper by showing that sea ice concentration and European temperature don’t correlate. However, this completely misses the non-linearity of the relationship. I think it’s fine to question the findings of the paper but I suspect that to “debunk”, or verify, the findings using the actual sea ice and temperature measurements you’d have to pick apart the contributions of other factors (e.g. polar jet changes, ENSO teleconnections) and then find some way of characterising the non-linear nature of the relationship with B-K sea ice.

ResearchBlogging.orgV. Petoukhov, & V. A. Semenov (2010). A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents Journal of Geophysical Research, 115 : 10.1029/2009JD013568

On “the real holes in climate science”

February 10, 2010

[This post is based on a question I got in response to a previous post but thought it deserved a short post on its own as there's a few interesting points.]

There’s been a lot of bad press recently for climate science but a lot of has focused on very minor issues. For example, most of the coverage on the UEA CRU email leak/theft/hack (so-called climategate) has focused on what some of the “skeptic” community wished was in the emails rather than what was really there. The Guardian has gone over some of the issues from the leak in depth in a recent series of articles, although this seems like a lot of focus on old issues. As Prof. Phil Jones himself said in a recent interview in The Sunday Times: “I wish people would read my scientific papers rather than my emails”. Glaciergate was equally blown out of all proportion given that the original claim only appeared in one sentence in a 3000 page report.

In the midst of all this, Nature printed a nice feature looking at the real big gaps in climate science (Schiermeier 2010), but it is behind a paywall, which is a shame because it’s a good piece. So, I thought I’d provide a very quick summary here.

Regional climate prediction

We still don’t have sufficient computing power to run models at high enough resolution to make projections on the scale that would be useful to policy makers. This is clearly required to make big infrastructure decisions.

Precipitation

Projections of precipitation patterns are really hard to make as they depend on temperature changes, circulation changes, radiative balance changes and pollution (and, therefore, cloud condensation nuclei) changes. Yet precipitation changes will probably have the biggest impact on society.

Aerosols

The effect of aerosols (i.e. small solid particles or liquid droplets suspended in the atmosphere) is a big unknown. Different types do different things and its not really certain whether they have a generally cooling effect – by reflecting away solar radiation – or a warming effect – by promoting more cloud growth and trapping more terrestrial heat. That said, any cooling effect would be very unlikely to reverse the warming impact of greenhouse gases.

The tree-ring controversy

This relates mostly to the “hockey stick” graph and the reliability of the palaeoclimate data we use to put our current climate into perspective. It’s important that we learn from past climate changes as we only have one atmosphere and can’t do experiments with it. But it is not easy to get palaeoclimate data (tree rings, ice cores, sediment cores) or to interpret them properly.

So what is the “consensus”?

In a certain sense, when people talk about the “scientific consensus about climate change” they really mean little more than our understanding of the greenhouse effect, our impact on it and that things are very likely to get messy in the future. All the details are still very much under investigation.

Reference:

ResearchBlogging.orgSchiermeier, Q. (2010). The real holes in climate science Nature, 463 (7279), 284-287 DOI: 10.1038/463284a

Skepticism or denial?

February 3, 2010

Whilst I would describe myself as a scientific skeptic, in that I will try to investigate claims before coming to a judgement, I would not say I was a “climate change skeptic”. This term is often used to label those that are irrationally dismissive of the scientific evidence (or worse). Several commentators on climate issues, notably George Monbiot of the Guardian, have now started referring to many within this group as “climate change deniers” as it appears that any amount of evidence counter to their stance will alter their belief in that position. One prominent blogger, though, found the use of the denial tag unhelpful and has set himself the challenge, as a layperson, “to make sense of the global warming and climate change debates” via a new blog.

Now, though, we have an opportunity to test the scientific integrity of one of these skeptics. Anthony Watts, an American weather presenter, blogger and self proclaimed climate change skeptic, was instrumental in setting up a web campaign to survey the United States climatological surface station records – SurfaceStations.org. This is a laudable scientific aim, regardless of the fact that it was done in the belief that it would show that the surface temperature recording method was flawed and that the warming trend observed in the US was an artefact of the local micro-conditions.

The analysis on the website consists of quite a lot of not-very-scientific comments about photographs on how poorly sited some of these stations are. Watts has also published a report with some of the photographs alongside their temperature records. However, Matthew Menne (a scientist at the American National Climatic Data Center) and co-authors have published a peer reviewed, systematic analysis of the US surface station temperature records. The results show that the poorly located stations, as determined by SurfaceStations.org, actually show a negative bias relative to the well located sites. This means that the poorly located sites introduce an artificial cooling in the temperature record, not a warming as Watts predicted. Clearly, the uncovering of such a bias in the surface station network in the US means that the infrastructure requires tighter regulation as it is not, at certain locations, doing its job properly.

In this situation, I suspect that a true skeptic would be proud that their effort had highlighted a real issue and contributed to the scientific understanding. However, as SurfaceStations.org approached their investigation with the hypothesis that the network would introduce artificial warming, how will they react?

Reference:

ResearchBlogging.orgM. J. Menne, C. N. Williams, & M. A. Palecki (2010). On the reliability of the U.S. Surface Temperature Record Journal of Geophysical Research : doi:10.1029/2009JD013094

Links:

The paper can be found here
There is a more thorough analysis of the paper by the Skeptical Science blog
There is some comment in The Guardian’s Environment blog

Glaciergate in perspective

January 18, 2010

The story is about a claim in the 2007 IPCC report that the Himalayan glaciers would melt by 2035.  It turns out that the evidence for this claim was from a speculative comment made by a not-very-prominent glaciologist in New Scientist in 1999.  The Times and The Express have gone to town with this story.  So, what does it really mean?

A little bit of background…

To understand the significance of Glaciergate, we first need to understand how the IPCC works.  So, the Intergovernmental Panel on Climate Change (IPCC) is split into 3 Working Groups:

  • WGI: The Physical Science Basis
  • WGII: Impacts, Adaptation and Vulnerability
  • WGIII: Mitigation of Climate Change


Each group produced a separate report in 2007.  They were each about 1000 pages long.  This was the fourth IPPC report round, the others were in 1990, 1995 and 2001.

WGI reviews and synthesises all the work on the physics and chemistry of the Earth system and tries to make projections of how things like temperature, rainfall and atmospheric circulation will change in the future.  I refer to this report a lot in my work as a meteorologist/climatologist.

I know a little about Working Group II – it is written by hydrologists, glaciologists, economists, social scientists and medical scientists – but I have very little idea about what goes on in WGIII.  I also confess that I’ve never looked at the WGIII report.  WGs II and III rely on a certain degree of speculation; it is their business to ask what the world would be like if certain things happen based on the projections from WGI.

Was the Himalayan meltdown a “central claim” in the IPPC report?

The 2035 date relating to the Himalayas appears in one sentence in Chapter 10 of the Working Group II report.  So this is one sentence in nearly 3000 pages. As far as I can see (please correct me if I’m wrong) the 2035 claim was not repeated in the WGII Summary for Policymakers or the overall Synthesis Report.  This was not a central claim.

Given that WGII is speculative by nature then Glaciergate appears to be a reviewing error rather than an attempt to distort the science.  Why the claim was given an implied “very likely” (90% certain) tag is worrying but then this is the first questioning of anything in the report that I can remember since it was published in 2007 – that says a lot for the skill and thoroughness of the report reviewers.

Most importantly, though, the WGII glacier claim changes absolutely nothing about the fundamental science behind climate change that appears in WGI.  This is like saying you wont trust anything in the economics section of The Times because they once printed a football result wrong.  The WGI science is all robust and, if anything, quite conservative in its claims and projections.

Dr Rajendra Pachauri (IPCC Chair) is a former railway engineer with a PhD in economics and no formal climate science qualifications…

Today’s Express also makes this statement as if it undermines the whole of the IPCC.  If anything, it just shows that the reporter has very little idea what the IPCC actually does.  Pachauri has worked in several different scientific disciplines and has headed a large organisation before.  In my mind, that more than qualifies him to head the IPCC.

Anyway, if you’re looking for people with in depth knowledge of specific fields, then there are the WG Chairs.  For example, WGI was chaired by Susan Solomon, who stands a pretty good chance of being awarded a Nobel prize for her work in the 1980s on the ozone “hole”.  Beneath the WG Chairs, each chapter has at least 1 co-ordinating author and 1 lead author.  Beneath them, each chapter also has many contributing authors, all experts in their field.

This attack on Pachauri doesn’t hold up very well.

The revelation is the latest crack to appear in the scientific concensus over climate change…

This claim was made in the Times yesterday, with the other cited cracks being the CRU email theft and something about sea level rise estimates.  This claim seems to assume that “consensus” means that no new work is going on in the climate sciences or at least demonstrates a complete ignorance of how science works.

Things will change in the science, which is exactly why the plans for the next IPCC report (due in 2014) are already well under way!  These are exciting (and, if I’m honest, a little depressing) times for climate science so its disappointing that many people outside the research community don’t want to know about it.

1 REASON WHY CLIMATE CHANGE IS MAN MADE

December 16, 2009

The front cover of yesterday’s Daily Express is shown below.  Oh dear.  As an atmospheric scientist, I reckon I could come up with more than 100 real scientific reasons why Earth’s climate changes naturally.  However, the Express article is more political than scientific and it doesn’t really reflect the headline.

Unfortunately, even if they had listed 1000 reasons why our climate changes naturally, it still wouldn’t undermine the 1 reason why most of the recent climate changes have happened because of our activities:

We have emitted millions of tonnes of greenhouse gases over many years.  These gases block outgoing heat from the planet.  We have evidence of “unnatural” climate changes in the recent past and fully expect much more in the future.  This point is not refuted by any of the 100 points given in the Express article.

Where to start on climate change?

December 13, 2009

Climate change usually only comes up in the media and online when there is some progress on a small detail or when something like Copenhagen or the UEA email theft happens.  I think that this presents a big problem as the people consuming these stories might not know the basic science yet, these days, everyone is expected to have an opinion on climate change.  This issue is amplified on the web where George Monbiot’s column on the Guardian website, for example, regularly receives more than 1000, usually anonymous and often controversial, comments.

So I thought it might be a good idea to write a quick blog post for a complete climate science beginner. I’m only going to tackle two questions here, skipping over quite a lot of things, but they are the key points to understanding climate change.

What are greenhouse gases and what to they do?

All our planet’s energy comes from the Sun.  Most of the radiation from the Sun goes straight through our atmosphere.  When Earth absorbs the Sun’s radiation the planet heats up and then re-emits a slightly different type of radiation.  The atmosphere can absorb this different type of radiation.  This keeps some of the heat near the Earth like a blanket, or a greenhouse.  The greenhouse effect is really important because without it the Earth would be much colder and our lives would be very, very difficult.  Most of this science was known by about 1850 – we’ve been working on the details since then.

How has the concentration of greenhouse gases changed?

Ironically, also by about 1850, the Industrial Revolution had really got going and people were beginning to burn lots of fossil fuels and change the make up of our atmosphere.  In particular, carbon dioxide was being released in great quantities.  Our best measurements of CO2, however, didn’t start until the 1950s in Hawaii (see graph).  This shows a really clear increase in atmospheric CO2.  This increase is having an affect on global temperatures because the greenhouse effect is keeping more heat in than it used to.

This is the climate change problem described in its most basic form – more greenhouse gases lead to a change in the energy that is retained from the Sun.  How this affects the Earth, though, is quite complicated (this why we talk about “climate change” more than “global warming” now) but the basic idea is quite simple.

Still want to know more?

If you still want to know more then I would say that the best place to start, as far as reliability and lack of agenda is concerned, would be the Intergovernmental Panel on Climate Change – this is a scientific group, organised by the UN, who review all the science relevant to climate change.  This is obviously a massive task but, nonetheless, they publish their reports in full online – the last science report came in at around 1000 pages long.  This is clearly not very easy to get to grips with.  However, the do produce a short and well written Summary for Policymakers that covers most of the big issues.  Also, they produce a Glossary where you can find the meanings of any terms you don’t understand.  I really hope that more people go and find out more about the interesting science behind our planet’s weather and climate!


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