The poor art of modelling climate change

What was Rob Vertessy, the Bureau of Meteorology’s Acting Head, thinking during his recent chat with ABC Radio Nation’s Fran Kelly about BOM-CSIRO’s State of the Climate Report 2012? He used race-track rhetoric to stress that the Bureau know everything they need to know about what drives climate change, and can make confident predictions. Did he have a flutter while studying for his doctorate in fluvial geomorphology at ANU, or during two decades researching catchment and forest hydrology at BOM?

RN: “Two consecutive La Niña weather events have caused a heat wave in Perth while the rest of the nation had a cool, wet summer. But lower temperatures and record rains do not signal a generally cooler or wetter climate. Global warming continues, according” to your report.

FK: “What is your finding on man-made input into these recent changes (unpredicted downpours) and how much are greenhouse gases contributing?”

RV: “We know (anthropogenic) carbon dioxide is the culprit. It’s a lay-down misere. There’s nothing to debate here.”

A misere is a trick-avoidance bid in card games where a player agrees to win no or a few tricks, usually indicating an extremely poor hand. A lay-down misere is a bid where a player is so sure of losing every trick that the player places his hand face-up on the table. In Australian gambling slang this might be referred to as a ‘dead cert’.

Yet there are some big questions that are not a ‘dead cert’. Where are the established laws of climate change? Will stabilising atmospheric CO2 concentration at 450 parts per million really limit global temperature increases to 2C? What evidence supports the ex cathedra claims of government agencies, such as “there is nothing to debate here” and “climate change is continuing…multiple lines of evidence show that global warming continues and that human activities are mainly responsible”.

Are they putting the confirmation bias cart before the scientific horse?

That the planet’s climate is changing is hardly news. Perhaps what punters need is a form guide on the climate’s causal linkages and the hard evidence supporting them?

In a speech at a U.K. House of Commons seminar last month, distinguished U.S. atmospheric physicist Richard Lindzen summarised the current state of knowledge:

“I will simply try to clarify what the debate over climate change is really about. It most certainly is not about whether climate is changing: it always is. It is not about whether CO2 is increasing: it clearly is. It is not about whether the increase in CO2, by itself, will lead to some warming: it should. The debate is simply over the matter of how much warming the increase in CO2 can lead to, and the connection of such warming to the innumerable claimed catastrophes. The evidence is that the increase in CO2 will lead to very little warming, and that the connection of this minimal warming (or even significant warming) to the purported catastrophes is also minimal. The arguments on which the catastrophic claims are made are extremely weak and commonly acknowledged as such. They are sometimes overtly dishonest.”

The jury seems to be still out on crucial aspects of climate attribution (causation), especially at the regional level, despite emphatic claims about settled and consensus science from the decarbonising crowd.

Another BOM-CSIRO partnership, the Centre for Australian Weather and Climate Research, admitted as much in its 2011 Technical Report 036: “the degree to which global warming may have enhanced heavy rainfall in some parts of eastern Australia remains uncertain”. The much promoted “current generation of climate models” gave “no clear guidance” as to whether the El Nino-Southern Oscillation (ENSO), one of the most important drivers of the continent’s weather and climate, “will change in response to global warming. Some models have strengthened ENSOs, some weaker, and others exhibit little if any change”.