Humans Undeniably Responsible for Pace of Climate Change

By Gemma Tarlach | September 27, 2013 12:11 pm

Scientists are more certain than ever before that human activity — from habitat destruction to fossil fuel burning — is behind the current pace and scope of climate change, according to a new report from the UN’s climate change panel, released earlier today.

The last three decades have been the warmest 30 years since the 7th century, according to the report, and anthropogenic, or human-driven, activity has been identified as the most significant cause. Since the Industrial Revolution of the 19th century, levels of carbon dioxide and other gases have risen at rates unprecedented in the preceding 800,000 years.

Human activity has been responsible for at least half of the increase in global average surface temperatures since 1950, the report concludes. The findings, by a working group of the Intergovernmental Panel on Climate Change (IPCC), are the first of four releases on the topic that will comprise the IPCC’s Fifth Assessment Report.

Growing Certainty

Although a two-page policymaker summary of the report is available in pdf format at the IPCC site, perhaps the most user-friendly version comes via Piers Forster, a prominent climate change researcher and IPCC contributor who reduced the dry 36-page document to 18 tweets, including:

Ocean has absorbed 90% of energy increase, warming virtually certain since 1900.

The direction of the IPCC’s report is not new: the organization has been monitoring climate change and researching how human activity influences it since the agency’s inception in 1988. What is striking about today’s report is the increase in data and improvements in observational methods that have allowed the group to makes its pronouncements with greater certainty than before. As reported on NPR:

The more scientists study this issue, the more confident they are that human activities are changing the planet.

The Future of Climate Policy

The Fifth Assessment Report, also known as the AR5, is the first full IPCC report since 2007. The release of the much-anticipated report puts climate change back on the front burner for both policymakers and the public, but some members of the scientific community question its ultimate utility. An editorial in the journal Nature argues that the IPCC would better serve its purpose by issuing shorter, more timely assessments:

It is time to rethink the IPCC. The organization deserves thanks and respect from all who care about the principle of evidence-based policy-making, but the current report should be its last mega-assessment.

The IPCC releases its assessment reports over the span of about a year; today’s release, formally known as the Working Group I: Physical Science Basis report, will be followed by three additional reports on related topics over the next 12 months.

Image by Durk Talsma / Shutterstock


CATEGORIZED UNDER: Environment, top posts
MORE ABOUT: climate change, IPCC
  • Creldarix

    “undeniably”. That doesn’t sound like open minded science to me.

  • Buddy199

    The IPCC revised its previous parameters for warming downward, contrary to the alarmism we’re used to.

    Also, they do not explain the 15 year pause in warming or why their models failed to predict it.

    So, the science isn’t settled. Not to the point that it can be used as justification to completely upend the world economy and the lives of billions.

    • m12345

      The problem is you, your misunderstanding of science.

      There was no 15 year pause, the energy as it states above, reduced to a tweet, 90% of the energy went into the ocean.

      I doubt you even understand your first sentence, let alone that the ECS was returned to the value it had prior to the previous report, and gives an average of 2.5-3 deg.

      Do you know what happens if the oceans warm even 1.5deg…

      • Buddy199

        That’s the hypothesis for the pause now, after the fact, that the models never predicted before the fact.

        The shifting temp range also indicates an incomplete grasp of the subject.

        The bottom line is there is a body of knowledge that’s pretty solid – global temp is rising – some that’s needs a lot more work – to what degree humans and other factors are respectively responsible – and the rest that we are still very uncertain about – long term predictions and specific consequences.

        Which makes climate science just like any other area of science. The “science is settled, move along nothing to see here” claim ludicrous, and unscientific in itself.

        • m12345

          You imply that climate scientists thought 100% of the energy stayed on land?
          This is a terribly presumptuous stance, considering the surface of the planet is 70% water.

          The minimum would be 70% of all incoming energy would be going into the water. But we also know land does not retain heat, it must go elsewhere.You either lose it or it goes into the water. Water temperature is a better indicator than land temperatures. Any one suggesting a 15 year pause based on just land based temperatures has only used less than 30% of the surface data.Would you trust a proposal based on less than 30% evidence?, as that is what the deniers want you to believe.

          The amount of modelling will get more accurate, but the message hasn’t changed. The message gets worse and worse the more data is added as models predicted.

          • Buddy199

            So what about the warming that hasn’t been happening since 1998? Here’s the key paragraph, buried on page 10: “The observed reduction in surface warming trend over the period 1998-2012 as compared to the period 1951-2012, is due in roughly equal measure to a reduced trend in radiative forcing and a cooling contribution from internal variability, which includes a possible redistribution of heat within the ocean.”

            After noting that scientists have only low or medium confidence in various theories for this reduced warming trend, the report adds that “there may also be a contribution from forcing inadequacies and, in some models, an overestimate of the response to increasing greenhouse gas and other anthropogenic forcing.”

            Translation: Temperatures have been flat for 15 years, nobody can properly explain it (though there are some theories), and the IPCC doesn’t want to spend much time doing so because it is politically inconvenient and shows that the computer models on which all climate-change predictions depend remain unreliable.

  • Norm

    The report claims “The last three decades have been the warmest 30 years since the 7th century,”

    This means it was warmer in the 7th century. There was no anthropogenic, or human-driven, activity which caused the warmth in that period. Doesn’t this suggest there may be other causes than anthropogenic for the current warming? Increased solar activity, cyclical warming etc.

    More importantly – why should average increased warming of 2 degrees Celsius over 100 years be considered a problem? Variations of 10 degrees in a single day are common. Couldn’t humanity adapt to such a minimally higher temperature?

    Horticulturists claim increased co2 is a benign condition, increasing plant yields. Tropical produce can be grown in regions further away from the equator.

    • disqus_atlq8Zmtsd

      Read: Antarctic Ice Sheets. Its a serious issue. I’m still skeptical as to how compelling the evidence is, but I certainly can appreciate the need to reduce pollution for reasons completely unconnected to global warming.

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    • JWrenn

      Actually it could mean that we can prove as far back as the 7th century this is the warmest, but we cannot not prove before that point. Couldn’t it?

      • Norm

        Hi J.

        I interpret your comments as a suggestion that they have no knowledge if it was warmer prior to the 7th
        century as they only have records from C 7 onwards.

        I pondered this point when I first read the article. They have introduced ambiguity in the statement.

        I decided that as they are definitely stating, “warmest thirty years since the 7th century”. The use of the word ‘SINCE’, implies to me that ‘PRIOR TO’ the 7th century it was warmer.

        Otherwise, they would have said since the 6th century or the 5th century or some other identifiable milestone in time. They stopped at the 7th century because that is the milestone of change in temperature.

        Importantly, if they use the words “sincethe 7th century”, they are deliberately including the Mediaeval Warm Period. (from around 800 to 1200 A.D.) (Wallace Broecker)

        What they are saying is that the last three decades have been the warmest 30 years since the 7th century, which includes the mediaeval warming period.

        The Press Release actually says,

        B.1 ATMOSPHERE

        “Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983-2012 was likely the warmest 30 year period
        of the last 1400 years. (medium confidence).”

        In summary, The panel has a MEDIUM LEVEL OF CONFIDENCE that the last thirty years was LIKELY to have been the warmest period of the last 1400 years.

        For your information, the press report explains, “A
        level of confidence is expressed using five qualifiers: very low, low, medium, high, and very high.”

        And assessed likelihood of an outcome or a result is expressed as

        virtually certain 99–100% probability, very likely 90–100%, likely 66–100%, about as likely as not 33–66%, unlikely 0–33%, very unlikely 0–10%, exceptionally
        unlikely 0–1%. Additional terms (extremely likely: 95–100%, more likely than not >50–100%, and extremely unlikely 0–5%)

        After all this time the panel is not telling us anything definite.


        • JWrenn

          Not no knowledge necessarily, but possibly not accurate enough knowledge or some sort of reason to not include it in their statement. From the rest of the press release it really just sounds like they have data from different sources that doesn’t fit in the current models, or seems to be in direct conflict with other information.

          As for not saying anything is definite…well welcome to honest science. If anyone says anything is definite on a panel of 1000 people I think they are full of crap. Really 95% means 950 people agree this is true and 50 don’t so that is about good with me considering how a panel works.

  • Betterose Ryan

    When viewed on a long time scale, 800,000 years is barely a scratch. What was the temperature like when the dinosaurs ruled the earth? And they roamed for far longer than 800,000 years. This is not to dismiss all of this but I find it interesting that we rely on a model that can’t accurately predict the past (unless things have changed) let alone the future. Lowering pollution is always a good idea but not at the expense of third world countries.

    • Ron Sonntag

      Sorry, but there are models that go back much further. And, there are geological records that roughly correlate temperature over the last 100+ million years.

      But, the issue is about what we have evolved with and what the current technologies for food production and distribution have to contend with. Also, climate is not regular. It is a chaotic system that is driven by many factors, and, like most chaotic systems, is subject to sudden jumps in behavior do to small changes in any one of those factors.

  • Ron Sonntag

    So, Creldarix, you would consider the undeniable link between smoking and cancer also unscientific? That has the same 95% certainty that climate change is being caused by humans.

    Also, everyone, yes there are many periods in earth’s history where the climate was warmer. These natural cycles are, with few exceptions, understood to be driven by orbital mechanics and other natural events (tilt of earth’s axis, precession of orbit around the sun, known major volcanic eruptions and asteroid hits).

    What is different about the last 100 or so years is that NONE of these natural drivers can explain the magnitude of temperature increase and rise in CO2. Read “The Two-Mile Time Machine” and you will understand and appreciate much more about what is happening.

    • Mark Stephens

      What about sun spots? Those explain the temp rise and have a direct correlation… I don’t trust the UN or any gov agency to be honest. Look at what happened to the American Indian.

      • Ron Sonntag

        Sun spots have an 11 year cycle. No, they do NOT explain the last 100 years.

  • Mark Stephens

    So wasn’t it warmer during the period of the Dinosaur? Did they drive cars and pollute?? They talk alot but have no definite proof. Only a fool would believe the government, ask the american indian!

    • Ron Sonntag

      The Government? The Government is US my friend. Millions of Americans working hard in the service of their country. Thousands of PhDs and extremely smart people who take their job seriously. You do them a grave injustice by dismissing their efforts. However, if you mean POLITICIANS, I have no quibble with your statement.

      And, yes, it was much hotter during the dinosaur period, AND, not a particular healthy place for humans!


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