The 2013 assessment by the Intergovernmental Panel on Climate Change released yesterday and preceded by last week’s press release in Stockholm, Sweden, minced no words when it stated that human influence on the global climate is clear.
According to the report, it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. The evidence for this has grown steadily thanks to more and better observations, an improved understanding of how the climate system responds to multiple triggers, and improved climate models. Those models have provided a better understanding of continental temperature analogies and the influences of anomalies such as volcanic activity that might lead to cooling.
Speaking of natural anomalies, the report recognized that the rate of warming in the last 15 years (1998-2012) which began with a strong El Nino is less than the rate of warming calculated since 1951. But a 15-year span does not reflect long-term trends. Effective climate models are based on a minimum of 30-year periods. Given climate complexities, variable temperatures should be normal and expected.
“Observations of changes in the climate system are based on multiple lines of independent evidence,” said Qin Dahe, co-chair of IPCC Working Group 1.
Variables notwithstanding, the atmosphere and oceans have steadily warmed, snow and ice have rapidly diminished, sea levels have risen, the concentrations of greenhouse gases have increased, and animal species are connecting the dots and making some lifestyle changes.
In the journal Nature Climate Change, a review of studies claims that animals are adjusting to a warming world by slight shrinkage in size. The study found that 38 of 85 animal and plant species had diminished in size over the past decades including squirrels, toads, red-billed gulls, shrimp, crayfish, and a sheep species in Scotland. While other variables could account for this, size shrinkage of animals has been found in the archaeological record when species adapted to periods of global warming in the past and a smaller body size helped shed body heat.
By the numbers, this 5th IPCC report is impressive. There were 209 lead authors and 50 review editors from 39 countries together with over 600 contributing authors with specific expertise from 32 countries. There were over 9,200 peer-reviewed scientific publications cited and two million gigabytes of numerical data from climate model simulations.
Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the northern hemisphere, 1983-2012 was likely the warmest 30-year period of the last 1,400 years.
It is virtually certain, the authors state, that the upper ocean (to a depth of 700 metres) warmed from 1971 to 2010 and was most likely warming steadily for the century prior to that. As sea ice and snow cover have continued to melt, sea levels have risen since the mid-19th century greater than the mean average rate during the previous 2,000 years. And CO2 emissions have stubbornly risen by as much as 40 per cent since pre-industrial times.
How much all this is going to get the attention of the Harper government, which has been notoriously lacking in effective policies on climate change, remains to be seen. The fed’s slash and burn approach to budgets for science research still stings. That short-sighted approach in an attempt to balance budgets denies the importance of continued research at a time when it is critically important to develop mitigation strategies.
“Continued emissions of greenhouse gases will cause further warming and changes to all components of the climate system,” said Thomas Stocker, co-chair of Working Group 1. “Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.”