In the last year, there were three major attempts to assess the current state of the science of climate change, as an update to the 2007 IPCC reports (which are already looking a little dated). They have very similar names, so I thought it might be useful to disambiguate them:

  • The Copenhagen Synthesis Report was put together at the University of Copenhagen to summarize a conference on “Climate change: Global Risks, Challenges and Decisions” that was held in Copenhagen in March 2009. The report has some great summaries of the research presented at the conference, and puts it all together to identify six key messages:
    1. Observations show that many key climate indicators are changing near the upper boundary of the IPCC range of projections;
    2. We have a lot more evidence now on how vulnerable societies and ecosystems are to temperature rises;
    3. Rapid mitigation strategies are needed because we now know that weaker targets for 2020 will make it much more likely we will cross tipping points and make it much harder to meet long term targets;
    4. There are serious equity issues because the impacts of climate change will be felt by those least able to afford to protect themselves;
    5. Action on climate change will have many useful benefits, including improvements in health, revitalization of ecosystems, and job growth in the sustainable energy sector;
    6. Many societal barriers need to be overcome, including existing social and economic policies that subsidize fossil fuel production and consumption, weak institutions and lack of political leadership.
  • The Copenhagen Prognosis was released in December 2009, put together as a joint publication of the Stockholm Environment Institute and the Potsdam Institute for Climate Impact Research. It focuses on the evidence behind the key issues for an international climate treaty, especially the target of limiting warming to 2°C, and the political actions necessary to do this. The key messages of the report are:
    1. The 2ºC limit is a scientifically meaningful one, because of the evidence about the damage caused by rises above this level;
    2. Even rises below 2°C will have devastating impacts on vulnerable communities and ecosystems (and for this reason, 80 nations have endorsed the idea of setting a global target to be “as far below 1.5ºC as possible”);
    3. Analysis of potential tipping points shows that currently discussed political targets will be unable to protect the world from devastating climate impacts and self-amplifying warming;
    4. Global greenhouse gas emissions must decline very rapidly after 2015, and reach net zero emissions by mid-century, if we want a good (75%) chance of staying below 2ºC of warming;
    5. The challenge is great, but not impossible – such a reduction in greenhouse gases appears to be technically feasible, economically affordable, and possibly even profitable (but only if we start quickly);
    6. The challenge will be especially hard for developing countries, who will need serious assistance from developed countries to make the necessary transitions;
    7. This will require unprecedented levels of North-South cooperation;
    8. Equitable allocation of carbon dioxide budgets suggest that industrialized nations must reach zero net emissions (or even negative emissions) in the 2020-2030 timeframe;
    9. Securing a safe climate for generations to come is now in the hands of just one generation, which means we need a new ethical paradigm for addressing this;
    10. The challenge isn’t only about reducing emissions – it will require a shift to sustainable management of land, water and biodiversity throughout the world’s ecosystems;
    11. The achieve the transformation, we’ll need all of: new policy instruments, new institutions for policy development and enforcement, a global climate fund, feed-in tariff systems, market incentives, technological innovations,
  • The Copenhagen Diagnosis was also released in December 2009. It was put together by 26 leading climate scientists, coordinated by the University of New South Wales, and intended as an update to the IPCC Working Group I report on the physical science basis. The report concentrates on how knowledge of the physical science has changed the IPCC assessment report, pointing out:
    1. Greenhouse gas emissions have surged, with emissions in 2008 40% higher than in 1990;
    2. Temperatures have increased at a rate of 0.19°C per decade over the past 25 years, in line with model forecasts;
    3. Satellite and ice measurements show the Greenland and Antarctic ice sheets are losing mass at an increasing rate, and mountain glacier melting is accelerating;
    4. Arctic sea ice has declined much more rapidly than the models predicted: in 2007-2009 the area of arctic sea ice was 40% lower than the IPCC projections.
    5. Satellite measurements show sea level rise to be 3.4mm/year over the last 15 years, which is about 80% above IPCC projections. This rise matches the observed loss of ice.
    6. Revised projections now suggest sea level rise will be double what the IPCC 2007 assessment reported by 2100, putting it at least 1 meter for unmitigated emissions, with an upper estimate of 2 meters; furthermore, sea levels will continue to rise for centuries, even after global temperatures have stabilized.
    7. Irreversible damage is likely to occur to continental ice sheets, the amazon rainforest, the West African Monsoon, etc, due to reaching tipping points; many of these tipping points will be crossed before we realize it.
    8. If global warming is to be limited to 2ºC above pre-industrial levels, global emissions need to peak between 2015 and 2020, and then decline rapidly, eventually reaching a decarbonized society with net zero emissions.

How long have we known?
Climate Science and Software Quality

2 Comments

  1. From the synthesis document:

    …increasing risk of social disruption through health impacts, water shortages and food insecurity.

    Most of the impacts discussed have little to do with global average mean surface temperature and much to do with regional climate patterns and local economic / political development. Lomborg’s criticism is spot on. Blaming everything on global climate change is a distraction to actually helping people who already have water shortages and food insecurity right now, and the reasons they suffer those things has nothing to do with the concentration of CO2 in our atmosphere.

    The ‘scientific research’ and ‘considerable support’ for defining dangerous levels of change weren’t actually references to any primary literature, but were references to previous government assessment or summary documents. I haven’t found any primary source that touts the 2C ‘guardrail’ (instruction / correction is always welcome though).

    [Lomborg's position is ridiculous (and deceitful). He's neither proposing to do anything specific to help people who suffer those problems right now, nor is he willing to consider how any solutions we do put in place in the short term will be sustainable in the face of serious climate change. I've asked many climate scientists why 2C, and none of them have a hard and fast answer, other than beyond that all bets are off as to when various feedback effects kick in. The issue was discussed extensively at the 2005 meeting on "Avoiding Dangerous Climate Change" - Steve]

    The observed temperature rise to date, about 0.7C, is already affecting health in many societies; the increasing number of extreme weather events, such as heat waves, floods, and storms, is leading to a growing toll of deaths and injuries from climate-related natural disasters.

    Really Steve? You think a statement like that has sound scientific evidence behind it?

    [Yes, I do. The IPCC WG2 gives a good summary. E.g. this table summarizes impact just on Asia - Steve]

  2. Interesting that you linked to WG2. While you are in Boulder you should ask the modelling boys how much capability their codes have for predicting a string of hot days or the frequency of regional droughts (or just attributing those things to deltas in CO2 concentration, that’s a difficult inverse problem).

    I respect your opinion about the soundness of the evidence for present and future catastrophe caused by climate change; it seems to be based on an earnest and thorough reading of the IPCC’s work.

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