Tag Archives: IPCC WGIII

IPCC Risk & Uncertainty

Posted on 21/04/2014 | Leave a comment

I haven’t had time to go into the latest WGIII IPCC report in detail (indeed I haven’t had much time recently to spend on blogging) but I had a quick browse through the report and there is an excellent chapter on “Integrated Risk and Uncertainty Assessment of Climate Change Response Policies” which goes through many of the key elements of current risk management theory and practise and how they can be applied to climate change.

A previous post highlighted the difficulties of making predictions given the uncertainties involved. The report highlights the “large number of uncertainties in scientific understanding of the physical sensitivity of the climate to the build‐up of GHGs” and acknowledges that these “physical uncertainties are multiplied by the many socioeconomic uncertainties that affect how societies would respond to emission control policies”. The report calls these socioeconomic uncertainties “profound” and lists examples as the development and deployment of technologies, prices for major primary energy sources, average rates of economic growth and the distribution of benefits and costs within societies, emission patterns, and a wide array of institutional factors such as whether and how countries cooperate effectively at the international level.

The IPCC gives a medium rating (50% probability) to the statement that the “current trajectory of global annual and cumulative emissions of GHGs is inconsistent with widely discussed goals of limiting global warming at 1.5 to 2 degrees Celsius above the preindustrial level”.

Included in Chapter 2 are the graphs below. According to the report “the representative concentration pathways (RCPs) are constructed by the IPCC on the bases of plausible storylines while insuring (1) they are based on a representative set of peer reviewed scientific publications by independent groups, (2) they provide climate and atmospheric models as inputs, (3) they are harmonized to agree on a common base year, and (4) they extend to the year 2100”. The 3 scenarios (A2, A1B and B1) are multi-model global averages of surface warming (relative to 1980–1999) shown as continuations of the 20th century simulations. Shading is the plus/minus one standard deviation range of individual model annual averages and the orange line is where concentrations were held constant at year 2000 values. Time permitting; it demonstrates that the conclusions and scenarios presented in the latest report are worth finding out more about.

click to enlargeIPCC global surface temperature scenarios from RCPs

Although each scenario is likely at the mercy of the uncertainties highlighted above, the open and thoughtful way the report is presented, including highlighting the underlying weaknesses, doesn’t mean that they (or the report) can be ignored. Indeed, the recent output from the IPCC will hopefully provide the basis for informed thinking on the subject in the coming years.

The report includes a reference to Kahneman-Tversky’s certainty effect where people overweight outcomes they consider certain, relative to outcomes that are merely probable. That implies that a 50% probability of the temperature blowing through 2 degrees celsius may not be enough to force real action. Unfortunately the underlying scientific and socioeconomic uncertainties inherent in making forecasts on temperature change over the next 30 to 50 years may mean that the required level of certainty cannot ever be achieved (until of course it’s too late).

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A quick look over the latest IPCC climate change assessment

Posted on 29/09/2013 | 3 comments

After the debacle of the last report, the spotlight is back on climate change with the release of the new (fifth) assessment by the Intergovernmental Panel on Climate Change (IPCC). The financial crisis, combined with credibility issues over the last report as a result of errors found after publication, has meant that the issue has taken a back seat in recent years. This assessment is drawn from the work of 209 authors with 50 review editors from 39 countries and more than another 600 contributors from across the global scientific community. It will hopefully dispel the nut job climate change deniers and allow for a renewed focus on concrete actions that can be taken to address climate change issues.

The latest publication from IPCC yesterday is actually a summary of headline statements and a “summary for policymakers” from the IPCC Working Group I which makes an assessment of the physical scientific aspects of the climate change. A full draft report will be published in a few days and is expected to be finalised by late 2013 or early 2014. The two other working groups, creatively named IPCC Working Group II and III, are due to publish their reports in 2014 and are charged with assessments of vulnerability to climate change and options for mitigating the effects respectively.

The language used by IPCC is important. For some reason they use a number terms for uncertainty, as follows:IPCC uncertainty

The strongest (and most obvious) statement is:

“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.”

It does sound silly that it has taken us this many years for a statement like that to be made unequivocally but that’s the world we live in. A graph from the summary from WG I is below.

IPCC findings

A number of the headline statements that are being reported in the press are included below.

Very high confidence is assigned to the ability of climate models “to reproduce observed continental-scale surface temperature patterns and trends over many decades, including the more rapid warming since the mid-20th century and the cooling immediately following volcanic eruptions“.

High confidence is assigned to each of the following:

  • “Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010.“
  • “Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.“
  • “The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia.“

Medium confidence is assigned to the assertion that in “the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years.”

Other strong statements include the following section (by the way, I think extremely likely is yet another new term meaning over 95% probability!):

“It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.”

The summary documents also refer to the scenarios used, including four new scenarios, to assess impacts on items including CO2, temperature, sea levels and temperatures. The full draft assessment and next year’s WG II and III reports will likely give more detail.

There is a few intriguing assertions in the report although they are subject to final copyedit.

Medium confidence is used to describe the assessment of whether human actions have resulted in an increase in the frequency, intensity, and/or amount of heavy precipitation. For the early 21st century and the late 21st century it is assessed that increased precipitation is likely over many land areas and very likely over most of the mid-latitude land masses and over wet tropical regions respectively.

Low confidence is used to describe the assessment of whether human actions have resulted in an increase in intense tropical cyclone activity and is also used to describe the likelihood of a change in intense tropical cyclone activity in the early 21st century.

The more detailed draft report from WG I will be interesting reading.

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