IPCC climate report: humans 'dominant cause' of warming


Climate change "threatens our planet, our only home", warns Thomas Stocker, IPCC co-chair

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A landmark report says scientists are 95% certain that humans are the "dominant cause" of global warming since the 1950s.

The report by the UN's climate panel details the physical evidence behind climate change.

On the ground, in the air, in the oceans, global warming is "unequivocal", it explained.

It adds that a pause in warming over the past 15 years is too short to reflect long-term trends.

The panel warns that continued emissions of greenhouse gases will cause further warming and changes in all aspects of the climate system.

To contain these changes will require "substantial and sustained reductions of greenhouse gas emissions".

Infographic Projections are based on assumptions about how much greenhouse gases might be released

After a week of intense negotiations in the Swedish capital, the summary for policymakers on the physical science of global warming has finally been released.

The first part of an IPCC trilogy, due over the next 12 months, this dense, 36-page document is considered the most comprehensive statement on our understanding of the mechanics of a warming planet.

It states baldly that, since the 1950s, many of the observed changes in the climate system are "unprecedented over decades to millennia".


PDF download IPCC Summary for Policymakers[3MB]

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Each of the last three decades has been successively warmer at the Earth's surface, and warmer than any period since 1850, and probably warmer than any time in the past 1,400 years.

"Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and that concentrations of greenhouse gases have increased," said Qin Dahe, co-chair of IPCC working group one, who produced the report.

Speaking at a news conference in the Swedish capital, Prof Thomas Stocker, another co-chair, said that climate change "challenges the two primary resources of humans and ecosystems, land and water. In short, it threatens our planet, our only home".

Since 1950, the report's authors say, humanity is clearly responsible for more than half of the observed increase in temperatures.

Dr Rajendra Pachauri said he was confident the report would convince the public on global climate change

But a so-called pause in the increase in temperatures in the period since 1998 is downplayed in the report. The scientists point out that this period began with a very hot El Nino year.

"Trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends," the report says.

Prof Stocker, added: "I'm afraid there is not a lot of public literature that allows us to delve deeper at the required depth of this emerging scientific question.

"For example, there are not sufficient observations of the uptake of heat, particularly into the deep ocean, that would be one of the possible mechanisms to explain this warming hiatus."

"Likewise we have insufficient data to adequately assess the forcing over the last 10-15 years to establish a relationship between the causes of the warming."

However, the report does alter a key figure from the 2007 study. The temperature range given for a doubling of CO2 in the atmosphere, called equilibrium climate sensitivity, was 2.0C to 4.5C in that report.

In the latest document, the range has been changed to 1.5C to 4.5C. The scientists say this reflects improved understanding, better temperature records and new estimates for the factors driving up temperatures.

What is the IPCC?

In its own words, the IPCC is there "to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts".

The offspring of two UN bodies, the World Meteorological Organization and the United Nations Environment Programme, it has issued four heavyweight assessment reports to date on the state of the climate.

These are commissioned by the governments of 195 countries, essentially the entire world. These reports are critical in informing the climate policies adopted by these governments.

The IPCC itself is a small organisation, run from Geneva with a full time staff of 12. All the scientists who are involved with it do so on a voluntary basis.

In the summary for policymakers, the scientists say the rise in ocean waters will proceed at a faster rate than we have experienced over the past 40 years. Global mean sea level rise for 2081−2100, the document says, is projected to be between 26cm (at the low end) and 82cm (at the high end), depending on the greenhouse emissions path this century.

The scientists say ocean warming dominates the increase in energy stored in the climate system, accounting for 90% of energy accumulated between 1971 and 2010.

For the future, the report states that warming is projected to continue under all scenarios. Model simulations indicate that global surface temperature change by the end of the 21st Century is likely to exceed 1.5 degrees Celsius, relative to 1850.

Prof Sir Brian Hoskins, from Imperial College London, told BBC News: "We are performing a very dangerous experiment with our planet, and I don't want my grandchildren to suffer the consequences of that experiment."

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  • rate this

    Comment number 378.

    Why do people continue to bury their heads in the sand even when the evidence is overwhelming?Well vested interests combined with public ignorance and an unwillingness to accept what is blatantly obvious has a lot to do with it.The simple fact is its easier and cheaper(in the short run) to plod on regardless!

  • rate this

    Comment number 377.

    The problem with the 'both sides' argument is that its about science. On one side we have scientists, and on the other side we have people who know nothing about science. There's a similar argument in the US about the age of the Earth. On one side we have scientists who've dated rocks accurately to 4.5 bn years old, and on the other side we have people who've read the bible.

  • rate this

    Comment number 376.

    Bubonic: "..IT consultants reviewed and fixed Y2K flaws and systems remained operational. " Please, the fact that the IT "consultants" conned num-nut politicians into surrendering billions of our money into a flick is well-known: countries which spend billions or zero had exactly the same outcome at midnight, i.e. NOTHING happened.

  • rate this

    Comment number 375.

    "Academic research is a waste of time. The problem with academic research is that it is peer reviewed."

    Who else is going to review them? Non experts? Experts are peers because the subject is a full time project. But, you are right.

    As I said earlier. The media needs to develop its own experts so that it can interrogate scientists from both sides of the fence. We need facts.

  • rate this

    Comment number 374.

    The UK government slaps on huge taxes on petrol & claims it is in the vanguard of green house gas emission control.

    Except it is all lies because all it has done is export manufacturing jobs to countries that exploit its workforce & the environment & then imports products back into the UK on oil burning cargo vessels.

    Net result bigger profits, mass UK unemployment, more global emissions.

  • rate this

    Comment number 373.

    Huge interest in this story, with many opinions

    But very soon this HYS will be closed and Matt McGrath will direct us to twitter, which is hardly a place for scientific debate even for those whose can be bothered with the gimmick

    The BBC wants to preach to us rather than allow debate, probably because many who contribute here know more about the science than the journalists

  • rate this

    Comment number 372.

    Has all the recycling us humans have been doing for years had and impact on the climate.

    I tend to hear about the climate change and all the bad news but not any good news, which makes me wonder are we making a difference???

  • rate this

    Comment number 371.

    "Trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends," the report says.

    So 15 years is to short a timescale to present reliable, but contradictory data to global warming, yet 50 years is acceptable ?

    We simply do NOT and CANNOT make predictions based on so little data. It will be millenia before we can do so.

  • rate this

    Comment number 370.

    It doesn't matter about global warming when you consider that our little rocky ball will get extremely hot and we will all be fried to a crisp over the next billion years or so. So can someone tell me why we should worry?

    My advice:- Use and abuse the planet while we still can!

  • rate this

    Comment number 369.

    The UK should try to be the world leader renewable industry. There's jobs to be had in R&D, manufacturing and exports.

  • rate this

    Comment number 368.

    Climate forecasts are about as reliable as economic forecasts.

    There are far too many micro-causes and emergent phenomena for us to accurately model the climate. It's ridiculous for these people to claim forecasts extending to the end of the century when they can't even model the absence of warming over the last two decades.

    We need "less politics in science and more science in politics"

  • rate this

    Comment number 367.

    I'm all for reducing emissions as much as possible. But in such a vast consumerist society how on earth do we do this. We set targets which often aren't met. Perhaps heft fines would make people more pro-active in curbing emissions. If you hit people where it hurts; their wallets, they might take things a bit more seriously. Use the money to invest in clean energy.

  • rate this

    Comment number 366.

    Bacteria. Over-reproducing,'taking',raping,garbage-machine,two legged stinking bacteria.
    That's what humans are. Just ask all the extinct & in-trouble.

  • rate this

    Comment number 365.

    This whole Man Made Global Warming nonsense is a crock.
    There is NO proof, there is NO evidence, there is NO consensus there is JUST a Theory which until proven is still just a Theory and if you have been told or believe otherwise then you do not know the first thing about the Scientific Method.
    When the Theory costs tax payers billions then the fact that it is just a Theory becomes a big issue.

  • rate this

    Comment number 364.

    I realise if we ignore the morons who say.. but what about this or how come the sun.. or but thousands of years ago.... then they feel they have won a counter argument by spouting some nonsense they made up while they were scratching themselves one evening.

    But why bother trying to educate such idiots as even with real evidence by people who actually know something they will remain ignorant.

  • rate this

    Comment number 363.

    Gobal warming is not actually happening - but still the bandwagon rolls on ignoring reality! This is not science but blind faith re-inforced by lavish funding and political support. Most despicable are the wealthy greens who want to stop economic growth, especially in third world countries and the closet racists who mutter about too many of 'these' people.

  • rate this

    Comment number 362.

    How sure were they Assad was guilty?

  • rate this

    Comment number 361.

    The UN report will be rubbished by those Climate Change denying obsessives who prefer to bury their heads in the sand. I've never understood people who deny science - be it climate change or evolution! I suppose they won't go away and we have to live with that. But now there is a clear report with excellent graphics, we can refer them to. But there's none so blind as those who will not see!!

  • rate this

    Comment number 360.

    Climate change is inevitable whether caused by humans or not.

    The average atmospheric temperature of the Earth over the past 600 million years is a full 11C warmer than it is today.

    The UN ruling to limit change to 2C is pure King Canute.

  • rate this

    Comment number 359.

    As remains of human habitation has been revealed by melting ice it might be fair to point out that mankind must have been through some of this climate change before. I have faith in nature and the human resourcefulness to adapt. Adaptation is the key to evolution In the past however it was a smaller population and less organised global control of people which prevents natural selection happening


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