Posts Tagged ‘satellite data’

How much does Antarctica contribute to sea level rise? (And how should that be communicated?)

October 26, 2012

There’s an interesting new paper in Nature (King et al.) this week that looks at how much the Antarctic continental ice contributes to sea level changes. It initially caught my eye as it uses data from the GRACE satellites, which are very cool! They are twin satellites that can detect tiny changes in the distance between one another. These distance changes are driven by changes in the gravity field so it is then possible to work out how that relates to changes in mass at Earth’s surface.

King et al. aren’t the first to use GRACE to look at Antarctic mass change but they have used a new model of the way ice sheets affect the Earth’s surface. When this new model is used, you get quite a low number for the contribution of Antarctic mass loss to global sea level: 0.19mm ± 0.05mm (this is less than half of previous GRACE estimates of Antarctic mass loss to global sea level).

The first result I found for global average sea level rise for 1993-2009 was: 3.3 ± 0.4 mm per year (thanks wikipedia!) so you can see that it is a small contribution.

Anyway, I tweeted a link to this paper from my @Antarctic_news twitter account and then noticed a story about the paper in the Sydney Morning Herald and tweeted a link to that as well.

Someone quickly pointed out that the headline in the SMH was wrong – it said Antarctica was contributing 1mm to global sea level when it should be less than that (0.19mm ± 0.05mm). It turned out that Ben Cubby, who wrote the SMH article, had already noticed the mistake (and our tweets) and the headline was corrected by the next day. This is why the article has a rather clumsy headline now!

But the chat on twitter didn’t end there. Quite a few tweets were exchanged between myself, Ben and Barry Woods, who felt that Ben should have said ~0.2mm per year in his article rather than “less than a millimetre per year”, which is what he did say (and was probably why the sub-editor made a mistake with the headline).

Personally, I feel that either (~0.2mm or less than 1mm) would have been ok so tried to defend Ben’s choice of words. Both options sound quite small and, without the context of average global sea level change (which I doubt many people hold in their head), the more accurate figure doesn’t really add much. Moreover, the full passage that includes the “less than a millimetre per year” bit gives some important qualitative information that does contextualise the result:

While the continent contains enough frozen water to raise global sea levels by 59 metres should it ever all melt, the findings show it is currently contributing less than a millimetre per year. Professor King said the findings showed that sea levels had already been rising faster than they had for centuries without much extra water from the Antarctic ice sheet.

That last bit, which I’ve emboldened, seems to convey that the Antarctic contribution is small in comparison to global changes without using either of the numbers (i.e. 0.19mm ± 0.05mm and 3.3 ± 0.4 mm per year).

Someone else suggested that is was in the interest of “environmental activists” to maximise the contribution of Antarctica to sea level rise but I’m not sure that even makes sense: the view from King et al. seems even more worrying i.e. sea levels are rising without a large contribution from Antarctica.

So what was the point of this blog post? Maybe it was so that I could articulate my thoughts without twitter’s 140 character limit but I was also wondering what other people thought about how to communicate findings like this. Should journalists always use the figures straight from papers or are phrases like “less than a millimetre” ok if they make the article more accessible?

King MA, Bingham RJ, Moore P, Whitehouse PL, Bentley MJ, & Milne GA (2012). Lower satellite-gravimetry estimates of Antarctic sea-level contribution. Nature PMID: 23086145

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Useful climate tools and data sites

January 11, 2011

Here are some links to useful climate data/tools. There’re my favourite places to get simple data.

If anyone uses anything different, please leave let me know!

KMNI’s Climate Explorer – excellent tool to get loads of data and basic plots. I’ve always found the inface friendly too.

NASA’s GISS Surface Temperature Analysis (GISTEMP) – raw station data and nice plotting tool.

UEA’s Climatic Research Unit have lots of data but no plotting tools.

Daily Earth Temperatures from Satellites – if you want satellite derived temperatures from various levels, this is the place to go.

NOAA’s National Climatic Data Centre – looks like there’s lots there but I’ve never really looked through it.

The University of Wyoming’s weather balloon data – probably a bit niche for this list but this is an amazing archive of balloon data from all over the world! Surely you need to check just how strong the Antarctic inversion is today? No?

The Icelandic volcano and weather

April 15, 2010

If you’re in the UK then I’m sure you’ve heard about the Icelandic volcano.  Its caused a shutdown of airspace in the UK as well as in Scandanavia and Holland because volcanic ash doesn’t mix well with aircraft engines.  The satellite image below shows the plume as of 10am on 15th April:

I just saw an interesting volcanologist on BBC News 24 explaining why this volcano is producing so much ash.  Apparently it’s because this volcano is beneath a glacier and this has led to the explosive eruptions that have sent the ash high into the atmosphere (up to the stratosphere).  An eruption from another Icelandic volcano earlier this month didn’t produce any problems as it wasn’t under a glacier and resulted in lava flows.  [Update: here’s a blog post about subglacial eruptions by a proper geologist.]

The interesting volcanologist also said that these eruptions can last anything from hours to years!

So it could be down to the weather to sort this one out.  The Met Office have issued a plot showing the location of the plume at 6am on 15th April.

If we take a look at the weather charts, we’re in a region of high pressure at the moment and this is drawing the ash south eastwards at the moment:

There’s not a lot of change tomorrow either so I doubt things will be much different then:

The high pressure moves eastwards a bit on Saturday so that may clear things away but I wouldn’t bank on it:

So it could be a while before the atmospheric circulation clears this ash away to make it safe for aviation.

On the plus side, this large injection of particles (aerosols) into the atmosphere could result in some really colouful sunsets – here’s an example – or even a blue moon.  These particle clouds can catch the light from the setting Sun at different heights to normal sunsets and this can be really beautiful!

Britain’s snow and climate change

January 8, 2010

NOTE: This post is from January 2010. I put a temperature anomaly plot from October 2010 here and I’ll do one for November 2010 as soon as the data is available.

I’m sure most of the Brits out there have seen this amazing NASA image of Britain covered in snow.  I love satellite images and use them a lot in my research – they really help me get a grasp of the big picture.

But what does this cold weather tell us about climate change?  Well, if we examine the whole northern hemisphere and look at how the temperatures for December compared to those from the last 30 years, then we get an interesting picture:

So, northern Europe and North America were colder than usual.  But southern Europe, Greenland, the Arctic and north Africa were all warmer than usual.  The situation for January will probably be quite similar.  So, looking at the bigger picture, the recent cold conditions in the UK don’t really tell us much about climate change – we need to look on big scales in both time and area.