Why aren't climate models better at predicting Arctic sea ice loss?

  • 17 Dec 2014, 01:20
  • Roz Pidcock

Climate models generally do a poor job of capturing how rising temperatures in the Arctic are affecting sea ice. Most underestimate the rapid pace at which sea ice is diminishing.

Why is that?

Scientists at the huge science conference hosted by the American Geophysical Union (AGU) taking place now in San Francisco have been discussing why it is so difficult to capture what's happening to Arctic sea ice in climate models, and how we can make the most reliable forecasts possible with the tools available.

A policy-making tool

Arctic sea ice extent has been declining by about  four per cent per decade, with the seasonal low at the end of summer shrinking particularly quickly.Screen Shot 2014-12-15 At 23.02.08 

Decadal trend in Arctic sea ice extent since 1979 (left) Map of changes in sea ice concentration across the Arctic (right) Source:  IPCC 5th Assessment Report (Sep 2013)

Reliable forecasts of how warming will affect sea ice are important for decision making, Professor Julienne Stroeve from the US National Snow and Ice Data Centre told the AGU conference. This includes questions like when the Arctic is likely to be sea ice free in summer.

But only a quarter of models simulate a rate of sea ice loss comparable with that observed by satellites since 1979, according to the  Intergovernmental Panel on Climate Change (IPCC).

So where are they going wrong?

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New satellite maps reveal hidden intricacies of Greenland ice loss and sea level rise

  • 15 Dec 2014, 20:00
  • Roz Pidcock

Jakobshavn Icebergs | B. Csatho

Greenland lost enough ice between 2003 and 2009 to raise sea levels by more than four millimetres, according to new research that maps the vast ice sheet in unprecedented detail.

Scientists have used satellites to measure ice loss at nearly 100,000 locations, concluding that the Greenland ice sheet is far more complicated that it's often assumed to be. And that means projections of how much we can expect sea levels to rise need updating.

Between 2003 and 2009, Greenland lost about 243 billion tonnes of ice a year, adding 0.68 millimetres to sea levels annually, the research finds. Almost half the ice lost came from Southeast Greenland.

Castho Et Al 2014_Fig3

Annual total ice loss from the Greenland ice sheet between 2003 and 2009. Source: Csatho et al., (2014)

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New paper raises question of tropical forest carbon storage

  • 15 Dec 2014, 16:00
  • Robert McSweeney

Tropical rainforest | P. Groenendijk

The world's forests provide a huge carbon sink, absorbing around a third of manmade carbon emissions, and helping to moderate global temperature rise.

A new study argues that the speed of tree growth in tropical rainforests isn't keeping pace with rising carbon dioxide levels in the atmosphere, and so it may be "too optimistic" to expect this buffering effect to keep pace with rising emissions.

But another scientist tells us the finding needs to be examined carefully, and it could be difficulties in taking measurements in tropical rainforests that are leading to the result.

Rainforests are an important carbon store

As part of the Earth's natural carbon cycle, vast amounts of carbon dioxide are taken out of the atmosphere and absorbed by the land each year. Tropical rainforests, the extremely productive forest ecosystems found gathered around the equator, are responsible for much of that exchange.

Through photosynthesis, trees convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their trunks and branches in the process.

Experiments scientists have carried out in temperate forests and greenhouses suggest that when there's more carbon dioxide in the air, trees can grow more quickly because their photosynthesis rate speeds up. This process is called 'carbon dioxide fertilisation'.

Scientists expect that as manmade carbon dioxide emissions increase, forests will absorb and store more carbon.

But a new study, published in Nature Geoscience, suggests that tropical rainforests might not be absorbing more carbon as emissions rise. Despite a 35 per cent increase in atmospheric carbon dioxide over the last 150 years, the study suggests that trees in the tropics aren't growing any quicker.

Studying tree rings

The researchers studied over a thousand trees of different ages, covering 12 different species and three different parts of the tropics. They chose areas of old-growth forests in Thailand, Cameroon and Bolivia that were undisturbed by deforestation or human settlements.

They analysed tall 'canopy' trees, which are the most common type in tropical forests and typically reach around 30 metres in height, and also smaller 'understorey' trees that grow to around 10 metres tall.

Examining tree rings can show how quickly a tree has grown from year to year. As a tree grows, it puts on extra layers of wood around its trunk, creating a new ring each year. The more a tree has grows in a year, the more wood it adds, and the wider the tree ring is.

800px -Tree _rings

Tree rings. Source: Creative Commons 2.5: Arnoldius

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Low carbon policies could cut household energy costs after 2030, Committee on Climate Change says

  • 10 Dec 2014, 00:01
  • Mat Hope

Windfarm in field | Shutterstock

Investing in low carbon energy generation could lower future household energy bills and insulate the economy from volatile fossil fuel prices, the government's official climate change advisor says. But only if the government commits to implementing long-term climate policies.

A new report from the Committee on Climate Change (CCC) assesses the impact of the UK's low carbon policies on consumer energy bills. It expects households to pay more to decarbonise the UK's energy sector in the coming decades, but says that doing so should ultimately save people money as well as helping the UK hit its legally binding climate goals.

The committee's conclusion mirrors that of  government analysis earlier this month that showed energy bills would rise significantly if the UK fails to implement climate policies.

Bill projections

The government is legally obligated to cut the UK's emissions, the committee points out. Some policies to cut emissions are paid for by households through a levy on their energy bills. While such levies are set to increase, decarbonisation should lower electricity prices in the long run and cut demand, meaning households save money overall, the committee says.

The Climate Change Act of 2008 requires the government to cut emissions  80 per cent by 2050. With about  35 per cent of the UK's emissions currently coming from the energy sector, that means some pretty significant changes to how the country generates electricity.

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European summer heatwaves ten times more likely with climate change

  • 08 Dec 2014, 16:00
  • Robert McSweeney

CC 2.0: Andrew Bowden

Climate change is raising the odds of summer heatwaves in Europe by a factor of 10, according to new research from the Met Office. Over the past 10 to 15 years, the likelihood of a 'very hot' summer has risen - from once every 50 years to once every five years.

As the frequency of heatwaves increases, so do risks to human health. Improving resilience to high temperatures is critical to avoiding deaths caused by extended periods of hot weather, the authors say.

A record heatwave

The summer of 2003 was the hottest ever recorded for central and western Europe, with average temperatures in many countries as much as five degrees higher than usual.

Studies show at least 70,000 people died as a result of the extreme high temperatures. In August alone, France recorded over 15,000 more deaths than expected for that time of year, a 37 per cent rise in the death rate. The same month also saw almost 2,000 extra deaths across England and Wales.

To see how climate change is affecting the likelihood of heatwaves and other extreme events, researchers carry out attribution studies. These identify the fingerprints of human influence on observed changes in temperature, rainfall, and other climate parameters.

The heatwave was the first extreme weather event to be attributed to the human influence on the climate, with research suggesting it was made more than twice as likely because of climate change.

Now a new study, published in Nature Climate Change, finds that recent warming means a similar heatwave is even more likely. The increasing impact of humans on the climate means the risk of 'extremely hot' summers is now ten times greater than when the 2003 European heatwave struck.

Very hot summers every five years

In the new study, Met Office researchers ran their climate models twice: first with both natural climate fluctuations and manmade warming included, and secondly with only natural influences on the climate. They compared the results to see how rising temperatures have altered the odds of heatwaves in Europe.

You can see in the left-hand chart below how close the model simulations that include manmade warming (black line) are to actual recorded summer temperatures (red line). By contrast, modelled summer temperatures from a world where there's no human influence on the climate don't match up well with what scientists are seeing.

This shows summer temperatures can't be explained by natural variability alone, and climate change is playing a role, the paper explains.

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Why the UN says climate adaptation could cost developing countries $1 trillion a year

  • 08 Dec 2014, 14:20
  • Mat Hope

Floods & sandbags | Shutterstock

Adapting to the worst impacts of climate change could cost three times as much as previous estimates, a new UN Environment Programme (UNEP) report suggests.

Developing countries may need to stump up anywhere between $250 billion and $1 trillion a year by 2050 to build flood defences, implement early warning systems, and develop more resilient farming techniques, it says.

We take a look at the figures, and explain why UNEP thinks climate adaptation costs are going to be hundreds of billions more than previous projections.


Last year, the Intergovernmental Panel on Climate Change (IPCC) released a major review of climate research. It said developing countries could expect to pay about $70 to $100 billion a year by 2050 to adapt to the worst impacts of climate change.

UNEP's new report says that is likely to be a "significant underestimate." It says adaptation costs for developing countries could reach $150 billion by 2025, and $250 to $500 billion a year by 2050.

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2014 on course to be the hottest year on record

  • 03 Dec 2014, 15:00
  • Robert McSweeney & Rosamund Pearce

UK Met Office

2014 is expected to be the among the hottest years since records began for the UK and the world, and may well prove to be the hottest, according to data from the World Meteorological Organisation (WMO) and the UK Met Office.

Rising temperatures are already contributing to greater risks of extreme weather, scientists warn.

A very warm and wet year for the UK

Met Office figures released today show the mean UK temperature for 2014 is 1.6 degrees Celsius above the long-term average. Currently 2006 is the warmest year since records began in 1910, but 2014 looks likely to replace it.

In England, where temperature records stretch back further, 2014 will be one of the warmest in the 350-year Central England Temperature (CET) record , the longest instrumental record in the world.

This year has also been a very wet one for the UK, and is on course to be the fourth wettest on record. A rainy December could even put 2014 over the annual record of 1337 mm set in 2000, says the Met Office.

A record-breaking year for the world

Globally, it seems likely that 2014 will be the hottest since records began in 1850. Average air temperature over the land and sea surface for 2014 so far is 0.57°C above the 1961-90 average. The previous high of 0.55°C warmer is held jointly by 2005 and 2010.

The ranking of hottest years is shown in the chart below. The red bars show years since the turn of the century, and show that for the most part the hottest years on record have occurred in the past decade or so.

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Meat and dairy consumption could mean a two-degree target is "off the table"

  • 02 Dec 2014, 23:59
  • Robert McSweeney

Wind turbine and cow | Shutterstock

Without a shift in meat and dairy consumption, limiting global temperature rise to two degrees is unlikely, says a new study by Chatham House.

The thinktank surveyed the meat and dairy eating habits of thousands of people in very different parts of the world. The findings show consumers underestimate the contribution of meat and dairy production to climate change, leading to them underestimate the effect that limiting meat and dairy consumption can have on limiting emissions.

The sizeable footprint of meat and dairy

The meat and dairy industry is responsible for 14.5 per cent of global greenhouse gas emissions. That's more than is produced by all cars, trains, planes and ships in the world.

Livestock emissions come directly from animals, from digestion and manure, and from transporting animals and producing their feed. Greenhouse gases are also released when forests are cleared to make way for pasture or for cropland in order to grow animal feed.

Chatham House _Livestock _Fig4

Livestock sector emissions by source. Chatham House.

China is the biggest consumer of both meat and dairy products, with the US, the EU and Brazil also in the top five. The top ten largest meat and dairy consuming countries are shown in the chart below.

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Europe’s energy and climate policies get mixed review

  • 01 Dec 2014, 11:00
  • Simon Evans

Windfarm | Shutterstock

The European Union is a global leader on climate change, but there's still plenty of room for improvement. That's the conclusion of a new energy policy review from influential thinktank the International Energy Agency (IEA).

The report summarises the big issues countries face when trying to decarbonise their energy sectors while keeping the lights on and preventing energy bill hikes.

It argues against schemes to pay power companies to ensure they're always ready to supply energy when required, such as the  capacity market currently being introduced in the UK. It also calls for a higher EU energy efficiency target, expanding  energy efficient policies, rapid  reform of EU carbon markets and caution when assessing  shale gas's potential contribution to the energy mix.  

IEA publications tend to be fairly weighty and this is no exception. We've picked out some of the most interesting findings and recommendations from its 312 pages.

Shale gas pessimism

Back in 2012 the IEA published a widely-referenced report setting out how hydraulic fracturing of shale rocks could deliver a new "golden age" of natural gas. It said Europe could expect to produce 77 billion cubic metres of shale gas per year by 2035, about the same as the UK's annual demand.

That outlook was pared back in 2013, when the IEA  said countries were failing to replicate the North American shale gas revolution. Its new review is even less optimistic. It says the EU has yet to evaluate the potential of shale gas and has only "limited" exploration experience.

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Education is "top priority" for climate change adaptation, study shows

  • 27 Nov 2014, 19:00
  • Robert McSweeney

Students in Swaziland | Shutterstock

Education does more to reduce deaths from climate-related disasters than economic growth, a new study finds. The researchers say education helps reduce vulnerability to disasters and enhances adaptation to climate change.

Financing adaptation

It's hard to pin down exactly how much money developing countries need to adapt to climate change. But some estimates suggest that it could be as much as $100 billion a year.

Countries have so far pledged $9 billion to the UN Green Climate Fund, which will provide money for adaptation and mitigation in developing countries.

Spending on climate change adaptation tends to be focused on large infrastructure projects, such as flood defences and irrigation systems. But new research, published in Science, suggests that investing in education could be a better way to reduce vulnerability to climate-related disasters.

Improving education reduces disaster deaths

The researchers argue that previous studies have concentrated too heavily on how economic development has reduced vulnerability to disasters such as floods, droughts and landslides.

They point to recent case studies that show improvements in education can give people the skills and knowledge to be better prepared for, and better able to recover from, natural hazards. For example, better-educated people in Cuba, Haiti and the Dominican Republic were faster at responding to hurricane alerts and recuperated more quickly once one had struck.

The researchers compare the influence economic growth and education have on the number of deaths from disasters for 167 countries across the world. They use Gross Domestic Product (GDP) per person as an indicator of economic growth and the number of women completing at least secondary school education as an indicator for education. They then cross-reference these with a database of climate-related disasters.

The results suggest that rising GDP has not reduced the number of deaths from climate-related disasters in the past four decades, while having a greater number of women in education has.

Better awareness of risk

So how does education reduce vulnerability to climate-related disasters? In an accompanying press release, co-author Dr Raya Muttarak explains:

"Education directly improves knowledge, the ability to understand and process information, and risk perception. It also indirectly enhances socioeconomic status and social capital. These are qualities and skills useful for surviving and coping with disasters."

Educated people have a better awareness of risk, the authors argue, and it gives them the knowledge and skills to adapt flexibly.

This is important because while scientists can make long-term projections of climate change, year-to-year weather variations mean they can't say exactly when a disaster will hit and how severe it will be. So a flexible approach to adaptation gives people and communities more capacity to cope when a disaster occurs.

Projecting future disaster deaths

When the researchers run simulations of future climate-related disasters, they find a similar pattern: improved education significantly reduces the number of deaths from disasters.

The results are shown in the graph below. The researchers use two pathways of how global education might change in the future: rapid expansion (red lines) and limited expansion (blue lines), which indicate, respectively, either substantial or minimal investment in education around the world.

The study models each education pathway against three scenarios of future change in climate-related disasters: no change (solid line), a 10 per cent increase (dashed line) and a 20 per cent increase (dotted line).

You can see that for each scenario of climate-related disasters, the improved education pathway results in fewer deaths.

The results suggest how "education is key in reducing disaster fatalities and enhancing adaptive capacity," says lead author Professor Wolfgang Lutz in the press release.

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