Thursday, September 20, 2012

Nature Editorial: Lambasts linkage of extreme weather to climate change.


Most of us Monitoring & Evaluation (M&E) professionals are acquainted with the problem of attribution. 

The attribution problem is often referred to as the central problem in impact evaluation. The central question is to what extent changes in outcomes of interest can be attributed to a particular intervention.

Attribution refers to both isolating and estimating accurately the particular contribution of an intervention and ensuring that causality runs from the intervention to the outcome.

So how do we establish impact? Most of the time, it is with comparison with the baseline. Baseline data (before the intervention) and end-line data (after the intervention) give facts about the development over time and describe “the factual” for the treatment group (not the counterfactual).

But changes observed by comparing before-after (or pre-post) data are rarely caused by the intervention alone, as other interventions and processes influence developments, both in time and space. Additional tasks of tracing impact back from interventions to specific (financial) contributions of different donors, are meaningless though this is what many terms of references require us to do.
Three related are problems are
1) establishment of a counter-factual;
2) elimination of selection effects and
3) problem of unobservables.  
Though we often could choose one among several methods - quantitative; experimental and/or quasi-experimental methods, many of these limitations remain or are compounded by using a combination of these methods.

So while M&E professionals frequently undertake often profitable impact evaluation studies, most of us do not take seriously our own findings.

Similar is the situation with climate change. While science illiterate NGO activists at the top of their hats attribute every extreme event to climate change; so far climatologists have not been able to establish it by hard scientific evidence.

A new paper in Nature this week goes right to the heart of the conversation about extreme events and their potential relationship to climate change. This is a complex issue and one not well-suited to sound bite quotes and headlines and so we give a gist of it here:   
  • Not all extremes are the same. Discussions of ‘changes in extremes’ in general without specifying exactly what is being discussed are meaningless. A tornado is an extreme event, but one whose causes, sensitivity to change and impacts have nothing to do with those related to an ice storm, or a heat wave or cold air outbreak or a drought.
  • There is no theory or result that indicates that climate change increases extremes in general. This is a corollary of the previous statement – each kind of extreme needs to be looked at specifically – and often regionally as well.
  • Some extremes will become more common in future (and some less so). We will discuss the specifics below.
  • Attribution of extremes is hard. There are limited observational data to start with, insufficient testing of climate model simulations of extremes, and (so far) limited assessment of model projections.
In short the paper concluded that attribution is a central problem and better models are needed before exceptional events can be reliably linked to global warming.

To read the full Nature paper on Extreme Events, Click here


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