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IPCC sea level rise projection probably too low, says expert survey

  • 22 Nov 2013, 18:30
  • Freya Roberts and Roz Pidcock

A new survey of expert opinion suggests 21st century sea level rise might be higher than the latest UN climate report projects. More than two thirds of the researchers interviewed for the study said higher and faster rises are possible - implying the report's estimates could be too conservative.

Upper limit underestimated

The most comprehensive projections on sea level rise are those contained in the  report from Intergovernmental Panel on Climate Change (IPCC). The IPCC evaluates evidence from all the published literature and combines the estimates into a single set of projections.

In its most recent report, the IPCC predicted sea levels are likely to rise by between 0.28m and 0.98m by 2100 - a range encompassing both its highest and lowest emissions scenarios.

But according to a new survey of sea level experts, that range might be an underestimate. Scientists from the Potsdam Institute of Climate Impact Research (PIK) asked 90 researchers from 18 different countries for their expert opinion on future sea level rise.

Two thirds of those questioned said they thought sea levels could rise higher than the IPCC's upper estimate for the end of the century.

When asked what they thought the likely range of sea level rise would be under a low emissions scenario, the experts came up with similar estimates to the IPCC.

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No time for delay in cutting greenhouse gas emissions, say IPCC scientists

  • 22 Nov 2013, 13:30
  • Roz Pidcock

As the end of the second week of climate talks draws nigh in Warsaw, a group of high profile scientists have laid out what needs to happen to stay below two degrees of global warming. The answer? Deep greenhouse gas cuts, and no more excuses for delay.

A matter of urgency

In its latest  report, the Intergovernmental Panel on Climate Change (IPCC) said limiting global warming requires "substantial and sustained" cuts in greenhouse gas emissions.

In a  new letter in Nature Climate Change, co-chair of the IPCC Thomas Stocker and Myles Allen from Oxford University consider two arguments used to suggest emission cuts can be delayed.

The first is that scientists have slightly lowered their assessment of how big the warming effect of carbon dioxide is on the planet - known as the climate sensitivity.

The other argument is that reducing emissions of pollutants like black carbon and methane is a more achievable way to limit total warming, instead of tackling carbon dioxide emissions.

The authors examine both arguments, concluding neither "buys time" to delay efforts to reduce carbon dioxide. Delaying emissions cuts now will make it harder to reduce warming in the long run, they say.

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Our work is unlikely to be last word on slowdown, say authors of new paper

  • 20 Nov 2013, 15:00
  • Roz Pidcock

Recent research suggesting the so-called slowdown in surface warming might be less than previously thought has been met with interest from both climate scientists and skeptics. We hear from the authors about some of the queries raised and why they think their research is not the final say on whether or not the "slowdown" is real.

A fresh look at global temperature

paper released last week challenged the idea put forward in the most recent IPCC report that there has been a so called "slowdown" in surface warming recently, saying temperature rise in the last decade and a half may be nothing unusual after all.

The authors of the new research used satellite data to essentially plug the holes in the Met Office's HadCrut4 temperature record where on-the-ground measurements are sparse. We reported on the new research  here.

The image below shows warming after 1997 in the original HadCrut4 data (thin red line) compared to the new, updated data (thick red line). The warming trend in the last decade or so is about two and a half times greater than without the corrections, say the authors.

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Q & A: Untangling the science on climate change and tropical storms

  • 19 Nov 2013, 14:45
  • Roz Pidcock

As aid finally reaches the stricken Philippines, the question of whether or not typhoon Haiyan can be linked to climate change has received more coverage this weekend.

With some pretty nuanced conclusions in the scientific literature and some selective deployment of those conclusions by parts of the media, it's become a tricky issue to navigate.

Here's a guide to some of the questions about climate change and tropical storms, and the sometimes quite complicated answers.

Was Haiyan a tropical storm, a typhoon or a cyclone?

All of the above. Tropical storm events are given different names depending on which ocean they form in. They are called hurricanes in the north Atlantic and northeast Pacific, typhoons in the northwest Pacific, and cyclones in the Indian Ocean.

Does the IPCC say there's no link between tropical storms and climate change?

No, it doesn't.

Scientific understanding of tropical storms is that they  derive energy from the warmth of the ocean and convert it into wind strength. Some of the heat trapped by greenhouse gases in the atmosphere is entering the oceans, causing them to  warm.

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2013 emissions edge the world closer to 2 degrees

  • 19 Nov 2013, 11:45
  • Freya Roberts

Carbon dioxide emissions are up again. This year's emissions are set to reach a record-breaking 36 billion tonnes, according to a new study from the Global Carbon Project.

News of the projected 2.1 per cent rise comes as negotiators at climate talks in Warsaw are discussing commitments to reverse the trend.

Researchers tracking emissions say the figures mean humans have used up more than 70 per cent of the global carbon budget, a figure that scientists estimate will give a reasonable chance of limiting global warming to two degrees.

All time carbon high

The  new study projects that emissions will rise 2.1 per cent in 2013, meaning more than 36 billion tonnes of carbon dioxide will be emitted over the 12 months in total. That's a record high for annual human emissions.

However, although emissions are still predicted to increase, the rate of increase is slower than the average over the past decade. Slower economic growth in countries like China are expected to contribute to this trend, say researchers involved with the project.

But even this slower rate of emissions growth is threatening the chance humans have of limiting global warming to the politically-safe target of two degrees Celsius.

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Not so slow “slowdown”? New paper says warming in last 15 years may be double what scientists thought

  • 14 Nov 2013, 16:15
  • Roz Pidcock

New research challenges the idea put forward in the most recent IPCC report that there has been a so called "slowdown" in surface warming recently, saying temperature rise in the last decade and a half may be nothing unusual after all.

The paper - which is an updated look at one the major temperature data sets the IPCC uses - suggests the rate of surface warming since 1997 is more than twice previously thought. But scientists tell us when you look a bit closer at the new data and the IPCC's numbers, the two aren't inconsistent.

IPCC on the "slowdown"

A big discussion point surrounding the latest climate report from the Intergovernmental Panel on Climate Change (IPCC) is how surface temperatures - that's the air above the land and oceans - have been rising relatively slowly over the past decade and a half.

The IPCC report put the rate of warming between 1998 and 2012 at  0.05 degrees Celsius per decade. That's quite a lot slower than the average of 0.12 degrees per decade since 1951.

In the report, this is given as an example of how natural climate variability can cause temperatures to rise faster or slower than than the long term average from one decade to the next.

But a  new paper, just published in the journal Quarterly Journal of the Royal Meteorological Society, takes a fresh look at one of the main datasets the IPCC uses, the Met Office's HadCrut4 temperature record.

The authors say correcting for well-known gaps in the dataset - to do with how much of the globe it covers - brings the rate of warming since 1997 up to 0.12 degrees Celsius. In other words, right in line with the decadal average.  

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Speculation over typhoon Haiyan link to climate change: A media roundup

  • 13 Nov 2013, 16:30
  • Roz Pidcock

Reuters

As a British aid convoy set out today for the Philippines, the media have posed the question of whether superstorm Haiyan can be linked to rising global temperatures. And some have done a pretty good job of explaining what the science says on this complex topic.

Typhoon Haiyan struck the Philippines four days ago and is  reported to have affected 6.9 million people. Winds reaching 310 kilometers per hour make the storm the  most powerful to make landfall since records began.

A warmer world

Tropical storm events are given different names depending on which ocean they form in. Tropical storms are called hurricanes in the north Atlantic and northeast Pacific, and typhoons in the northwest Pacific. Tropical storms are also sometimes called cyclones.

As this  Guardian piece describes, tropical storms derive energy from the warmth of the ocean. And the surface ocean is warming. In its latest report, the UN Intergovernmental Panel on Climate Change (IPCC)  said the top 75 metres of the ocean warmed 0.11 degrees between 1971 and 2010.

It would seem to make sense that such storms get stronger as the surface of the ocean warms. That's the theory, at least. But what do measurements of storm activity tell us?

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How vulnerable is the energy sector to extreme weather?

  • 12 Nov 2013, 12:15
  • Freya Roberts

Sourced under creative commons

Since the 1950s, the world's seen an increase in the number and intensity of many extreme weather events, which can be challenging for the infrastructure that powers our society.

As the climate changes, we are also contemplating transforming energy systems. So what effect will changes in climate extremes have on energy infrastructure? That's the question examined in a newly published special issue of the journal Climatic Change.

Extreme events in the 21st century

The latest report from the Intergovernmental Panel on Climate Change (IPCC)  suggests some types of climate extremes are becoming more severe as the climate changes.

In its Fifth Assessment Report, the IPCC  concluded the world had experienced more hot days and nights, more heat waves, and more heavy rainfall events since the 1950s. Similar patterns are projected for the future too, as are changes in the way damaging events like hurricanes occur, although with less certainty.

 

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A blagger's guide to the Warsaw climate talks

  • 11 Nov 2013, 16:30
  • Robin Webster

Thousands of government delegates and lobbyists will spend the next two weeks crowded into a conference hall in Warsaw, Poland, attempting to inch the international community one step closer to a climate change deal.  

Haven't we been here before?

The answer is yes, pretty much every year. The conversation has been going on for some time. Negotiations on a deal on climate change were launched back in December 1990 and the UN Framework Convention on Climate Change (UNFCCC) was formally created four years later. 

191 countries are now 'parties' to the convention. And every December, all the parties meet up for a two-week negotiating session. This year, it's Poland's turn to host. 

Aim of the talks 

The ultimate aim of the talks is to stabilise greenhouse gas concentrations in the atmosphere "at a level that will limit dangerous interference with the  climate system". In order to achieve that, the participating countries have to agree to targets limiting their future greenhouse gas emissions. 

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Did the Montreal Protocol contribute to the surface warming slowdown?

  • 10 Nov 2013, 21:00
  • Freya Roberts

A ban on gases that created a hole in the ozone layer may have contributed to the slowdown in surface warming, if new research is right. An international team of scientists says that cuts in CFC gases agreed under the Montreal Protocol lowered surface temperatures since the 1990s.

CFCs and the slowdown

A few decades ago chlorofluorocarbons (CFCs) were found in everyday objects like fridges and plastic packaging. That was until scientists discovered the gases were causing a hole in the ozone layer. In 1987 countries from around the world signed the  Montreal Protocol, an international agreement to phase out CFCs.

According to a new study in the journal Nature Geoscience, the international agreement had an unintended consequence for earth's climate. The authors of the study spotted it when looking at the links between the rate of global warming and the speed at which greenhouse gas emissions were increasing.

Their analysis showed that emissions and temperatures had been rising and falling in sync since 1880. In the 1960s there was a jump in both emissions and warming, marking the start of a period of more sustained global warming. Then in the 1990s that warming slowed.

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