Climate change forecasts used as the basis of policy and billions of pounds in investment worldwide are flawed, according to new research from Lancaster University Management School (LUMS).
The new study, by Robert Fildes and Nikolaos Kourentzes at the Lancaster Centre for Forecasting, applies the latest thinking on forecasting to the work of climate change scientists.
And it says that while their research results add further evidence of global warming from a forecasting perspective, there is only limited evidence of a link between annual emissions of CO2 and the 10- and 20-year rise in global annual average temperatures
Claims from competing interest groups have led to a decline in confidence in statements on climate change - particularly in the wake of allegations of manipulated data from the University of East Anglia, and incorrect projections on Himalayan glaciers.
The Lancaster research aimed to make 10 and 20 year ahead climate predictions more accurate and trustworthy for policy-makers, and be the basis for more informed debate over the realities of climate change.
Besides demonstrating that current forecasts are not as accurate as they could be, the researchers argue that a sole focus on limiting greenhouse gases may be a mistake.
The report, released today, explains: “The scientific community of global climate modellers has surely taken unnecessary risks in raising the stakes so high when depending on forecasts and models that have many weaknesses.
“In particular, the models may well fail in forecasting over decades (a period which is beyond the horizons of most politicians and voters), despite their underlying explanatory strengths.
“A more eclectic approach to producing decadal forecasts is surely the way forward, together with a research strategy which explicitly recognizes the importance of forecasting and forecast error analysis.”
The study, published in the International Journal of Forecasting, added: “Of all of the areas of forecasting that have succeeded in gaining public attention, the current forecasts of global warming and the effects of human activity on the climate must surely rank amongst the most important.
“Even before the Kyoto treaty of 1997 there was an emerging scientific consensus on global warming identified with the Intergovernmental Panel on Climate Change (IPCC). By the time of the Fourth Assessment Report in 2007, few scientists working in the field did not accept two central tenets from the IPCC’s work: that the earth was warming and that some part of the warming was due to human activity.
“Nevertheless, there have long been powerful counter-voices, both political and scientific, which either denied the first tenet or accepted it but did not accept that human activity was a major causal force.
“In the political sphere, for example, both the Australian Prime Minister John Howard, in office from 1996 to 2007, and the USA President George W. Bush, from 2001 to 2008, dismissed the notion of global warming.
“From a scientific perspective, a disbelief in global warming is found in the work of the Heartland Institute and its publications, and supported by the arguments of a number of eminent scientists,
some of whom perform research in the field.
“The continuing controversy raises questions as to why the 4th Report is viewed by many as not providing adequate evidence of global warming.”
The research team said they set out to review the various criteria used to appraise the validity of climate models, and in particular the role of forecasting accuracy comparisons, and to provide a forecasting perspective on this important debate which has so far been dominated by climate modellers.
The authors said: “We focus on decadal forecasts (10–20 years ahead). Such forecasts have many policy-relevant implications for areas from landuse and infrastructure planning to insurance, and climatologists have shown an increasing interest in this 'new field of study'.
“Decadal forecasts also provide a sufficient data history for standard forecasting approaches to be used.
“We first set out various viewpoints underlying the notion of a ‘valid forecasting model’, particularly as they apply to complex mathematical models such as those used in climate modelling.
“The evaluation of such models is necessarily multi-faceted, but we pay particular attention to the role of forecasting benchmarks and forecast encompassing, an aspect neglected by climate modellers generally, as well as by the IPCC Working Group.
“In particular, we examine the effect on the forecasting performance of including CO2 emissions
and CO2 concentrations... that links emissions as an input with global temperatures as an output.
“These results are contrasted with those produced by Smith et al. (2007) using one of the Hadley Centre’s models, HadCM3, and its decadal predictive variant, DePreSys.
“By considering forecast combining and encompassing, it is shown that the trends captured in the time series models contain information which is not yet included in the HadCM3 forecasts.
“While our results add further evidence of global warming from a forecasting perspective, there is only limited evidence of a predictive relationship between annual emissions of CO2 and the 10- and 20-year ahead global annual average temperature.
“However, looking to the conclusions, simple forecasting methods apparently provide forecasts which are at least as accurate as the much more complex GCMs for forecasting the global temperature.”
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