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What the IPCC report says about extreme weather events

  • 11 Oct 2013, 15:30
  • Freya Roberts

The world has already witnessed more hot days and heat waves since the 1950's - and the new IPCC report warns we'll see more changes to weather extremes by the end of 21st century. But a close look at the report reveals that rising temperatures won't affect all kinds of extreme events in the same way.

Here's a quick run through of what the latest report from the Intergovernmental Panel on Climate Change (IPCC), says about hot days, heat waves, hurricanes and heavy rain - past and future.

What's the big deal about extremes?

Extreme events expose humans to conditions beyond the realms of what we're used to. That could be unusually high temperatures, sudden heavy downpours, or longer lasting droughts. If people and the infrastructure we rely on can't withstand these abnormal conditions, the economic and human losses can be huge.

Take the 2003  European heatwave. It had devastating human consequences, with tens of thousands of people estimated to have died when temperatures rose above 40 degrees Celsius for a number of weeks. Or look at superstorm Sandy last year: the economic losses are thought to be in region of  $50 billion.

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Apocalypse norm: 'Climate departure' assessment prompts doomsday media coverage

  • 10 Oct 2013, 15:45
  • Carbon Brief Staff

A new piece of scientific research pinpoints when global temperatures are set to exceed the bounds of natural variability, pushing the world into a new climate normal.

The paper puts forward a slightly different perspective on future climate change to most research, which tend to focus on what impacts we're likely to see from climate change by a given time.

The research is in  Nature, a major journal, which yesterday hosted a press conference covering the findings, and it's been written up by the newswires. So it's perhaps not surprising it's attracted a bit of media coverage today. But depending on which news article you read, you might end up with a different take on how dramatic the findings are.

A new normal

The research looks at when the global average temperature will consistently stay above the bounds of natural variability experienced since 1860.

Using projections from 39 climate models, the researchers find that if we continue to emit greenhouse gases at current rates, we'll reach this point of 'climate departure' by 2047.

By mid-century, while the coldest years could be similar to the sort of thing we see today, the average temperature will be higher than even the hottest years of the last 150 years.

And even if greenhouse gas emissions slow to a complete stop by the end of the century, we will only delay reaching this climate shift by about 20 years, according to the paper.

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What the new IPCC report says about sea level rise

  • 03 Oct 2013, 15:25
  • Freya Roberts

Sourced under creative commons

Scientists' best guess on sea level rise this century has increased considerably on its last  projections in 2007. The Intergovernmental Panel on Climate Change (IPCC)  now estimates seas will rise between 26 and 82 centimetres.

So what's changed?

Best estimates

Between 1901 and 2010, global sea levels rose by 19 centimetres - an average of about 1.7 millimetres per year. But looking at the last few decades, it's clear sea level rise is speeding up. Between 1993 and 2010, sea levels rose by 3.2 mm per year - almost twice the long term average.

Since the 1970s (at least), it's very likely that there has been a human contribution to the rise in sea levels, the report  states. 'Very likely' here means the IPCC considers there is a 90 per cent chance.

With greenhouse gas emissions set to continue rising, the IPCC projects more and faster sea level rise by the end of the 21st century. Exactly how much will depend on how we choose to address climate change, as the graph below shows.

The IPCC's four new scenarios of future climate change, called the Representative Concentration Pathways (RCP), all assume some carbon cuts take place - with the exception of the highest emissions scenario RCP8.5.

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What the new IPCC report means for Europe

  • 01 Oct 2013, 16:10
  • Freya Roberts

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Europe has been warming faster than the global average over the last 30 years, the UN's new climate report reveals.

Yesterday afternoon, the Intergovernmental Panel on Climate Change (IPCC) released part one of its scientific report in full.

Among some of the most significant findings from a summary of the report released a few days ago are that humans are responsible for at least half of the warming experienced in recent decades. The report also predicts higher sea levels and further warming worldwide if greenhouse gas emissions continue.

The full report also looks at how climate change could pan out differently across the many regions of the world. There will be much more on this when the IPCC releases the second part of its climate report in March 2014. But the first part provides some valuable insights about how climate change affects  Europe.

Changes so far

Since 1979, the land in Europe has been warming faster than the global average of 0.27 degrees Celsius (°C) per decade - but some parts have been warming faster than others.

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Scientists react to today’s UN climate report

  • 27 Sep 2013, 17:45
  • Roz Pidcock

Today an international group of hundreds of climate scientists released a report covering how and why the earth's climate is changing, and how it may change in the future.

We wrote a summary of the report's top findings and a simple background for everyone. But how has the report been received by the scientists involved? We asked a few for their reaction.

Scientists are 95 per cent confident that humans are changing the climate

The topline from the new report - and one many media outlets have picked up on - is that scientists can now say with extremely high confidence the world is warming and that humans have been the dominant cause of that warming since the 1950s.

Dr John King from the British Antarctic Survey tells us:

"[T]he message I would want people to take home is increasing certainty that human activity has been having an impact on climate and will continue to do so into the future, that we are now able to make predictions with increased confidence"

King adds a note about how confidence in this message has grown stronger in recent times, saying:

"I think it's interesting to look at this in the context of the whole series of IPCC assessments that have come out. We're now on the fifth one and over time the message that has become stronger and stronger that there is a measurable human impact on climate ...The message hasn't changed, it's just being delivered with greater and greater confidence as the evidence base has accumulated"

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IPCC: Six graphs that explain how the climate is changing

  • 27 Sep 2013, 16:30
  • Freya Roberts

After a week spent meticulously agreeing the exact wording, the Intergovernmental Panel on Climate Change (IPCC) has just released a summary of the first part of its major report reviewing the science of climate change.

Known as the '  Summary for Policymakers' (SPM), the document describes the physical science behind climate change - whittling down the latest findings about how and why earth's climate is changing to just 36 pages.

It also makes predictions about how temperatures and sea levels might change in the future - relative to their average levels between 1986 and 2005. The two main ones we'll touch on here are RCP2.6, a low emissions scenario where carbon emissions are rapidly cut, and RCP8.5, a high emissions scenario with no carbon cuts.

But who can be bothered to read a 36 page document? So here are 6 pictures (okay, graphs…) to give you the gist.

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Carbon Brief's guide to the IPCC report

  • 27 Sep 2013, 13:45
  • Freya Roberts

As global greenhouse gas emissions continue to rise, the earth is warming, snow and ice is melting, and sea levels are rising. These are the confident conclusions from a brand  new report from the Intergovernmental Panel on Climate Change (IPCC).

The full report runs to several thousand pages, but scientists have distilled its contents into a 36-page summary - intended to capture the findings most relevant to policymakers. Here are the bits you need to know about:

Temperatures

One of the clearest signs of climate change is rising temperatures. Between 1880 and 2012, earth's surface warmed by approximately 0.85°C, and the first decade of the 21st century was the hottest since modern records began in 1850. Scientists are 95 per cent certain humans' influence on the climate is the dominant reason earth warmed between 1951 and 2010.

The report notes that within the long term warming trend, short periods of slower surface warming have occurred. Between 1998 and 2012, for example, earth's surface has warmed at a rate of 0.05°C per decade - which is slower than the trend since 1951 of 0.12°C per decade.

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UK media gear up for major climate report

  • 23 Sep 2013, 18:00
  • Roz Pidcock

With a week until the UN's climate body releases its new report on how and why the climate is changing, the media are limbering up in anticipation. Here's a quick look at who saying what.

Although the full report from the Intergovernmental Panel on Climate Change (IPCC) is not yet in the public domain, the draft version of a draft guide for policymakers was  leaked to  journalists a few weeks ago.

Scientists and policymakers are discussing the wording of the summary in Stockholm this week, and a final version is due for release on Friday morning.

"Stark warning"

The report looks set to increase the certainty with which scientists can point to human influence on climate change - and this forms the backbone of some of the coverage.

A two-page spread in yesterday's  Observer carries the headline 'IPCC issues stark warning over global warming'. The piece lays out what appears to be the top finding from the new report: scientists are surer now than ever human activity is the biggest source of warming since the 1950s.

With the help of a handy 30-second explainer on the IPCC, the BBC reports this morning:

"Scientists will underline, with greater certainty than ever, the role of human activities in rising temperatures."

While a lot of the discussions about the new report are likely to concentrate on temperatures at earth's surface, the evidence for warming is stacking up in other areas too. Ice sheets are dwindling, the oceans are warming and sea levels are rising, reported yesterday's  Independent:

"[D]raft pages show that in addition to temperature rises, changes are being observed throughout the climate system."

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Less than one metre or up to two? Predicting sea level rise in the 21st century

  • 19 Sep 2013, 09:00
  • Freya Roberts

Leaked versions of the UN's coming climate report suggest the forecast for sea level rise will be higher than previously thought. According to a new article in the journal Nature, the report could predict "close to one metre" of sea level rise by 2100. But even that might be a lowball, according to some climate models which suggest a rise of up to two metres can't be ruled out.  
We explain how the latest sea level rise forecasts are made, and why some scientists feel the threat could be even greater than the IPCC's report looks set to suggest.

An upward revision

While the physics of how human-caused warming can drive up sea levels have been understood for a  long time, the science of predicting how fast sea levels will rise is less certain.

The last IPCC report, published in 2007, predicted sea levels would rise by between  18 and 59 centimeters by the last decade of this century. But according to leaked versions of the forthcoming report seen by the  some media outlets, the IPCC has estimate has revised that estimate upward.

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A pre-IPCC recap of the links between extreme weather and climate change

  • 17 Sep 2013, 17:20
  • Roz Pidcock

With just over a week to go until the UN's new climate report is released, media stories are beginning to be written anticipating the report, and a series of leaks from the notoriously leaky review process have provided ample fodder for those who want to put their own spin on things.

Today's  Telegraph gets a few things wrong in examining what scientists know and don't know about the link between extreme weather and climate change.

Yesterday,  the paper uncritically reproduced the argument of a piece in the  Mail on Sunday which claimed that the IPCC's estimate of how much the world has warmed since 1951 has halved since the last report in 2007.

That claim appears to be  wrong, but the Telegraph piece  this morning repeats some of the arguments - as well as some new ones about the link between extreme weather and climate change.

Hurricanes, droughts and floods

Let's focus on what the new IPCC report apparently says about  rising global temperatures and hurricanes, droughts and floods. Writing in the Telegraph, journalist Bruno Waterfield says:

"The EU has often linked extreme weather events to global warming after the IPCC said six years ago that it was more than 50 per cent sure that hurricanes, flooding and droughts were being caused by manmade global warming. That figure is expected to be revised down to less than a 21 per cent certainty that natural disasters are caused by climate change."

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