Analysis

Rising air temperatures caused Antarctic ice shelf collapse

  • 11 Sep 2014, 19:04
  • Robert McSweeney

Larsen-B Ice Shelf | Shutterstock

The collapse of a giant ice shelf in Antarctica in 2002 was the result of warmer air temperatures new research concludes, allowing scientists to identify two clear ways in which ice shelves become unstable.

Single summer

At the beginning of February 2002, the Larsen-B ice shelf stretched across 3,250 square kilometers, an area larger than Luxemburg. By the end of the following month it was gone.

In the space of a single Antarctic summer the entire 220-metre thick ice shelf disintegrated into the sea.

Since the dramatic collapse, scientists have been trying to understand how the shelf could disappear so quickly.

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Greenhouse gas concentrations hit record high

  • 09 Sep 2014, 16:23
  • Robert McSweeney

Mauna Loa | Shutterstock

Greenhouse gas levels in the atmosphere reached a record high in 2013, according to the latest measurements by the World Meteorological Organisation.

As announced in their annual Greenhouse Gas Bulletin, the amount of carbon dioxide in the atmosphere has reached 396 parts per million (ppm) - 42 per cent higher than pre-industrial levels.

Largest increase

The World Meteorological Organisation's (WMO) measurements revealed an increase in global carbon dioxide concentrations from 2012 to 2013 of almost 3 ppm. This is larger than recent annual increases of around 2.1 ppm and the largest annual increase since 1984.

The steady increase in annual carbon dioxide over the past 30 years is shown in the upper graph below. These increases are primarily caused by burning fossil fuels such as oil, coal and gas, but cement production, deforestation and land use change also contribute.

The lower graph shows how the annual increase, or growth rate, has varied over the same period. It shows the peak in 2013 and also an earlier spike in growth rate in 1998, which was the result of widespread wildfires during a strong El Niño event.

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Scientists may have solved a climate change mystery using Greenland ice cores

  • 04 Sep 2014, 19:09
  • Robert McSweeney

Greenland Camp | Oregon State Uni

Scientists have long known that carbon dioxide is the main cause of most of the warming we've seen since pre-industrial times. But there are periods in the Earth's distant past when the connection between carbon dioxide and temperature rise has been harder to see.

New research into Greenland's ice sheets now seems to have explained one of the mysteries of our climatic past, confirming the importance of carbon dioxide on global temperature changes.

Mystery interval

Around 20,000 years ago the Earth was emerging from an ice age as orbital changes meant it received slightly more of the sun's energy.

As ice sheets melted into the oceans, sea levels rose and ocean circulation patterns changed.

Scientists think these changes caused carbon dioxide from the oceans to be released into the atmosphere.

Yet despite the planet being closer to the sun and higher levels of carbon dioxide, records for Greenland didn't seem to show much change in temperature. While the rest of the northern hemisphere appeared to warm, Greenland didn't seem to follow suit for another 3,000 years. Scientists couldn't explain why, and it was even dubbed the 'mystery interval' by one study.

But now the new study published in the journal Science suggests that temperatures actually had risen - but the rise wasn't captured by earlier ice core records.

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Is there enough water to frack?

  • 03 Sep 2014, 12:40
  • Mat Hope

Derrick rig: Shutterstock

There are many reasons policymakers across the world have been casting envious glances at the US's shale gas boom: from falling energy prices to curbing emissions. But a range of geological, economic, and social obstacles have made it  tricky to replicate elsewhere.

A new  report from the World Resources Institute (WRI) thinktank highlights another: water availability.

Getting shale gas or oil out of the ground can be very water intensive. Knon as fracking, it involves shooting large amounts of water and chemicals into the shale rock to create fractures through which the resources can be pumped. The  International Energy Agency estimates it could require anywhere between a few thousand to 20 million litres of water per well.

That's a problem, the WRI says, as many of the countries with the largest shale resources don't have much water to spare.

Water availability

For the first time, the WRI has mapped global water availability alongside the location of the world's shale resources. It finds that 38 per cent of the countries thought to have the largest shale resources also have strained water supplies.

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How the IPCC is sharpening its language on climate change

  • 01 Sep 2014, 17:40
  • Simon Evans

Barometer | Shutterstock

The Intergovernmental Panel on Climate Change (IPCC) is sharpening the language of its latest draft synthesis report, seen by Carbon Brief.

Not only is the wording around how the climate is changing more decisive, the evidence the report references is stronger too, when compared to the previous version published in 2007.

The synthesis report, due to be published on 2 November, will wrap up the IPCC's fifth assessment (AR5) of climate change. It will summarise and draw together the information in IPCC reports on the science of climate change, its impacts and the ways it can be addressed.

We've compared a draft of the synthesis report with that published in 2007 to find out how they compare. Here are the key areas of change.

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Some important context on Arctic sea ice melt

  • 01 Sep 2014, 16:31
  • Robert McSweeney

Iceberg | Shutterstock

The Mail on Sunday  reports that Arctic summer ice is on the increase, disproving the "myth of Arctic meltdown".

But the article, by journalist David Rose, acknowledges a declining trend in summer Arctic sea-ice. And scientists tell us the increase in ice is natural year-to-year variation.

Climate change is warming the Arctic, and scientists think it will make the region ice-free in summer at some point this century - points that despite the hyperbolic headline, the Mail on Sunday notes.

Ice gain or loss?

The Mail article reveals "how melt has slowed over ten years" using the graph below, showing Arctic sea ice extent from 2004 to 2014.

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In brief: How much do volcanoes influence the climate?

  • 29 Aug 2014, 12:00
  • Roz Pidcock

Overnight, a volcano in Iceland called Bardabunga began erupting, triggering a flurry questions about the possible impacts for the UK and further afield.

In 2010, Eyjafjallajökull eruption in Iceland  disrupted global transport - shutting down air traffic across Europe for several days.

Volcanoes also have an effect on the climate. Throughout earth's history, volcanic eruptions have punctuated the temperature record. We take a quick look at the role of volcanic eruptions in climate - past, present and future.

A tiny contribution to global warming

Volcanic eruptions can affect climate in two main ways. First, they release the greenhouse gas carbon dioxide, contributing to warming of the atmosphere.

But the warming effect is  very small. Volcanic carbon dioxide emissions since 1750 are at least 100 times smaller than those from fossil fuel burning, according to the latest report from the Intergovernmental Panel on Climate Change (IPCC).

A two-year cooling effect

As well as carbon dioxide, volcanic eruptions also blast a cloud of ash, dust and sulphur dioxide into the stratosphere, which is quickly blown around the globe.

Sulphur dioxide combines with oxygen and water to form sulphuric acid "aerosols". These particles directly reflect sunlight and encourage clouds to form.

This cooling effect outweighs the warming contribution from carbon dioxide, causing an overall cooling that tends to lasts for about two years after a major eruption.

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Widespread methane leakage found on US Atlantic coast

  • 26 Aug 2014, 15:39
  • Robert McSweeney

New research has found evidence of methane leaking from under the sea floor on the Atlantic Coast of the US. Could this be the beginnings of a huge release of methane into our atmosphere? Scientists tell us probably not.

Seabed seeps

The research has identified hundreds of 'seeps' along the American Atlantic coast - places where gas bubbles out of the sea floor. This could be just the beginning, with perhaps "tens of thousands" more seeps to discover, the researchers say.

They also say it's likely the bubbling gases include methane - a powerful but short-lived greenhouse gas. Methane stored under the seabed is one of the largest reserves of methane on the planet - a companion article describes the overall size of the reservoir as "staggering".

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Pacific watch: Is El Niño finding its second wind?

  • 22 Aug 2014, 14:55
  • Roz Pidcock

Scientists around the world have been watching closely to see if an El Niño develops this year - a weather phenomenon in the Pacific that drives extreme weather worldwide.

After initially predicting with  90 per cent certainty we'd see an El Niño by the end of the year, forecasters began scaling back their predictions earlier this month.

But interest in the Pacific weather phenomenon shows no sign of waning. And after much talk of El Niño cooling off, there are hints it could be rebounding, say scientists.

El Niño watch

Every five years or so, a change in the winds causes a shift to warmer than normal ocean temperatures in the  equatorial Pacific Ocean - a phenomena known as El Niño.

Together, El Niño and its cooler counterpart La Niña are known as the El Niño Southern Oscillation (ENSO). Between them, they're responsible for most of the fluctuations in global temperature and rainfall we see from one year to the next.

Earlier this year, the ocean looked to be primed for an El Niño, with above average temperatures in the eastern Pacific lasting throughout March and May.

But last month, forecasters across the world began  dialling down their forecasts. The atmosphere had "largely failed to respond" to sea surface temperatures, scientists announced.

"Waiting for Godot"

This week, the US National Oceanic and Atmospheric Administration (NOAA)  dropped the odds of an El Niño developing in autumn or winter to 65 per cent, down from 80 per cent  earlier this month. As NOAA scientist, Michelle L'Heureux,  described recently:

"Waiting for El Niño is starting to feel like Waiting for Godot"

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Surface warming ‘hiatus’ could stick around for another decade, say scientists

  • 21 Aug 2014, 19:00
  • Roz Pidcock

A flip-flopping natural fluctuation in the Atlantic is behind a recent slowdown in surface warming - and it's not due to reverse for another ten years, according to new research.

The theory outlined in a paper  published today in the journal Science disagrees with other research, which pins the blame for the so-called "pause" on changes in the Pacific.

We talked to some other scientists working in the field - and they don't seem convinced.

Puzzle solving

Scientists know greenhouse gases are driving up  global temperature. But data on land and  the surface of the ocean shows  slower than expected warming in the last 15 years or so.

Periods of slower and faster warming  aren't unusual. Scientists say the main reason we're seeing one now is because more heat is finding its way to the  deeper ocean, rather than staying at the surface.

But which ocean? Knowing where the heat is ending up might help scientists predict how long the hiatus will last.

Where Is Global Warming Going _infographic

More than 93 per cent of the heat reaching earth's surface goes into the oceans. Just 2.3 per cent stays in the atmosphere. Source: Skeptical Science

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