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Have satellites overestimated Antarctic sea ice growth?

  • 22 Jul 2014, 15:30
  • Roz Pidcock

It's puzzling why Antarctic sea ice seems to be growing while earth's other icy expanses are shrinking as temperatures rise.

Now new research questions whether there has been much of a rise in Antarctic sea ice after all. The paper suggests the small but significant growth scientists thought had occurred since 1979 could be little more than a "spurious artifact" of how satellite data is interpreted.

But other polar scientists tell us the implications of the new findings" are very limited indeed" and they're confident Antarctic sea ice is still growing.

Bucking the trend

Scientists know ice is being lost from both the Greenland and Antarctic ice sheets. They also know the amount of sea ice in the Arctic is rapidly decreasing.

But satellite data suggest the amount of sea ice around Antarctica has been growing since 1979. A report from the Intergovernmental Panel on Climate Change (IPCC) last year put the size of the increase at  1.5 per cent on average per decade.

For comparison, that's about a third of the rate of sea ice retreat in the Arctic. A  new paper just published in journal The Cryosphere explains the puzzle this poses for scientists:

"[T]here has been substantial interest in the trend in Antarctic sea ice extent … primarily because of the observed asymmetry between increasing ice extent in the Antarctic and rapidly diminishing ice extent in the Arctic, and the inability of current climate models to capture this."

The new paper raises an interesting point. It notes that the growth in Antarctic sea ice in the latest IPCC report is much bigger than suggested in the previous one in 2007. The authors say:

"[The 2007 report] reported the trend in Antarctic sea ice extent to be small and statistically indistinguishable from zero".

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Slow surface warming since 1998 is “not exceptional”, say scientists

  • 21 Jul 2014, 19:30
  • Roz Pidcock

Scientists know greenhouse gases are causing the world to warm. But an interesting question is why warming at earth's surface speeds up and slows down.

new paper shows surface temperature "slowdowns" like we're experiencing now aren't unusual - and capturing the timing of natural ups and down in the climate is key to predicting them.

But as a  second paper explains, the planet as a whole has warmed up in the last decade even as surface temperature rise has been sluggish.

Model mismatch

Temperatures are rising due to long term greenhouse gas warming. But natural variability causes temperatures to go up and down from one year to the next.

Natural variability can at least partly explain slower surface warming in the last 15 years, the Intergovernmental Panel on Climate Change (IPCC)  concluded in its latest report. Recent evidence  points to changes in the  Pacific causing the deep oceans to absorb more heat.

But most climate models didn't predict the slowdown. And as a  new paper in Nature Climate Change explains, some parts of the media have argued that since models don't replicate recent temperatures, we shouldn't trust their predictions for future warming.

But the paper, lead by Australian climate scientist Dr James Risbey, finds that 15 years of temperatures rising slower than models predict "does not constitute evidence against the fidelity" of models in general. Let's take a closer look at why not.

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Typhoon Haiyan, record-breaking CO2 levels, rising seas and more: five measures of the state of the climate in 2013

  • 18 Jul 2014, 17:00
  • Ros Donald

Atmospheric carbon dioxide levels broke modern records last year - and 2013 was one of the warmest years on record according to four major datasets. Sea levels continue to rise, and the oceans are getting warmer. The US National Oceanic and Atmospheric Administration's State of the Climate, 2013 is a reminder of the many changes the world is experiencing. 

The State of the Climate report, published by the Bulletin of the American Meteorological Society, is a different beast to the Intergovernmental Panel on Climate Change's (IPCC) fifth assessment report. Both reports assemble multiple datasets to give a picture of the changes the planet is experiencing, but NOAA's annual climate checkup doesn't try to answer why certain events have occurred. Instead, it focuses on building a detailed picture year on year, chronicling the shifting state of the physical climate system. 

NOAA has also created a  summary that pulls out the report's most striking results. We've picked five measures that help form this picture along with NOAA's explanation of why they matter. 

 

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Climate change spells bad news for reindeer, say experts

  • 17 Jul 2014, 11:40
  • Roz Pidcock

If you look at one corner of the Arctic, you might conclude climate change means reindeer are better off. But those that benefit are likely to be the exception rather than the rule, say scientists.

Overall, warming is leading to loss of habitat, food and declining reindeer populations.

Svalbard reindeer

According to an article in yesterday's  Times, reindeer numbers are growing on the Norwegian islands of Svalbard.

The piece is based on data from scientists at the Arctic University of Norway, who have monitored reindeer populations in Adventdalen Valley on Spitsbergen, Svalbard's main island, since 1979.

The new research suggests the reindeer of Svalbard may be doing OK out of climate change, as melting ice reveals new grazing territory. But this is the latest estimate from one group of researchers, and not all scientists are as confident of such a rosy picture.

Getting a handle on reindeer numbers in these vast and remote landscapes is difficult. This Smithsonian  feature from March explores researcher Steve Albon's efforts to monitor reindeers in Svalbard, where he says the impact of climate change is not yet well understood.

Reindeer in decline

Svalbard is just one part of the Arctic where reindeer live. And the picture looks very different in some other parts.

Reindeer _map _ABT2010

How reindeer populations are faring across the Arctic. Green is increasing, red is decreasing and orange is unknown. Source:  Arctic Biodiversity Trends 2010

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The future of coal in China, India, Australia, the US, EU, and UK

  • 16 Jul 2014, 13:00
  • Mat Hope

CC: Bobak

Have reports of coal's demise been greatly exaggerated? It depends which part of the world you look at.

Global coal use has grown significantly over the last decade, with global demand increasing 60 per cent between 1990 and 2011, according to research body the International Energy Agency (IEA). With some countries implementing climate policies to limit the use of polluting fuels, some commentators are predicting  coal's imminent demise.

Bp Global Coal Consumption

Source:  BP Statistical Review of World Energy

That's probably premature. While some European countries are ramping up renewables, shutting coal plants and closing mines, other parts of the world are planning an extraction frenzy to feed emerging economies' seemingly insatiable energy demand.

Here's a quick guide to coal's prospects around the world.

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Arctic summer sea ice is disappearing fast, but can we rescue it?

  • 14 Jul 2014, 15:30
  • Roz Pidcock

Diminishing Arctic sea ice is perhaps the most iconic consequence of climate change. And there's a good chance we'll lose it in summer before too long if emissions stay high, according to a new paper. But its demise is not a foregone conclusion - with a swift peak and decline in greenhouse gases we could still reverse that trend, the scientists say.

Losing ice

Arctic sea ice cover is declining by about  four per cent per decade. But the seasonal low in summer is shrinking particularly quickly, at more like 11.5 per cent per decade.

At the other end of the planet, Antarctic sea ice is growing - but much slower than it's being lost in the Arctic. We've written more about global sea ice loss  here.

AR5_summer _Arctic _sea _ice _extent

Arctic sea ice summer extent has decreased by between 9.4 to 13.6% per decade. Source: IPCC 5th Assessment Report,  Summary for Policymakers

 

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What’s your city doing to protect you from climate change? In six charts

  • 10 Jul 2014, 16:45
  • Roz Pidcock

From London to São Paulo, half the world's population resides in huge urban metropolises. But living in some cities will be worse for your health than others. New research pinpoints more than 200 cities leading the way in tackling climate, protecting citizens and businesses along the way.

Is yours one of them?

Cities under pressure

Cities are hubs of economic and human activity. They house at least 50 per cent of the world's population and produce more than  80 per cent of its gross domestic product (GDP).

But the concentration of people and assets make cities vulnerable when disaster strikes. In its  latest report, the Intergovernmental Panel on Climate Change (IPCC)  warned of an increasing risk to cities from climate change, through rising temperatures, increasing frequency and severity of heatwaves, and greater risk of flooding. Coastal cities also have to deal with rising sea level rise.

But cities are taking the initiative in tackling climate change, according to a  new report from the Cities Climate Leadership Group (  C40). It looked at what 207 cities across the world are doing to alleviate climate change's impacts.

Waking up to climate change threats

Cities Report Infographic

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Climate scientists tell us why it’s “utterly, utterly normal” to have a paper rejected

  • 09 Jul 2014, 13:30
  • Roz Pidcock

TimesdissentAn  article in yesterday's Times featured claims that a climate scientist's work was "censored" because it "questioned the accuracy of computer models used to predict global warming".

Rather less excitingly, what actually happened was an "utterly, utterly normal" example of peer review in action, scientists tell us.

The scientist involved agrees that the journal's comments were correct, and his paper was subsequently published - it's available here.

So what's the story?

Accusations of censorship

The Times  article - entitled 'Voices of dissent drowned out by climate change scientists' discusses research German climate scientist Vladimir Semenov submitted to the Journal of Climate in 2009.

Ben Webster, an experienced environment correspondent, suggests parts of Semenov's paper were "deleted" before publication because they represented a "voice of dissent". Webster says:

"The paper suggested that the computer models used by the UN's Intergovernmental Panel on Climate Change (IPCC) were flawed, resulting in human influence on the climate being exaggerated and the impact of natural variability being underplayed."

Semenov is quoted as suggesting the journal's intervention amounted to "some kind of censorship". Had the paper not been revised, it could have had "profound implications", the Times claims.

 

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Factcheck: What’s the significance of a record high in Antarctic sea ice?

  • 07 Jul 2014, 16:20
  • Roz Pidcock

Sea ice around Antarctica is growing, and it's a scientific puzzle. But while the Mail on Sunday suggests this means climate change is less of a problem than scientists say, sea ice is only part of what's going on in Antarctica, and the world as a whole is losing ice rapidly.

A record high

An article in yesterday's Mail on Sunday carries the headline:

'Global warming computer models confounded as Antarctic sea ice hits new record high'

This follows news last week from scientists at the University of Illinois that the area covered by sea ice surrounding Antarctica hit a record high on 29th June, with about two million square kilometres in June more ice compared to the long term average.

Antractic Sea Ice _June 2014

Antarctic sea ice reached a record high in June, with 2.1 million square kilometres more than the long term average. Source: US National Snow and Ice Data Centre ( NSIDC)

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Six things to know about Antarctic ice

  • 07 Jul 2014, 15:00
  • Roz Pidcock

This article was originally published in November 2012.

When scientists talk about ice and climate change, it's often about how quickly it's disappearing. So recent  news stories  about Antarctic sea ice growing may come as a surprise. 

The amount of ice in the ocean around Antarctica is indeed increasing, but this is only part of what's going on in the Antarctic as a whole. We've put together six things you should know about climate change and Antarctic ice.

1. Antarctic waters are warming faster than the global average

Along with the rest of the world, the Antarctic is warming up. The Southern Ocean, which surrounds the continent of Antarctica, has been warming faster than the rest of the world's oceans since the 1950s, at a rate of  0.17 degrees Celsius compared to a global average of 0.1 degrees. The increased rate of warming is mainly due to the way large weather systemstransport heat to the poles.

2. Despite rapid warming, there's more Antarctic sea ice

Despite rapidly warming water, the amount of ice that floats on the Southern Ocean around Antarctica - known as sea ice - is slightly increasing. On 26 September 2012, the USNational Snow and Ice Data Centre (NSIDC) confirmed that Antarctic sea ice reached a record extent - a measure of sea ice cover - of 19.44 million square kilometres.

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