A report released in a scientific journal, Climate Risk Management, analyzed the chances that factors other than human influence are driving global mean temperature change.
“December 2013 was the 346th consecutive month where global land and ocean average surface temperature exceeded the 20th century monthly average, with February 1985 the last time mean temperature fell below this value,” researchers noted in their abstract. “Even given these and other extraordinary statistics, public acceptance of human induced climate change and confidence in the supporting science has declined since 2007.”
They write, “The degree of uncertainty as to whether observed climate changes are due to human activity or are part of natural systems fluctuations remains a major stumbling block to effective adaptation action and risk management.”
The writers develop an approach “which provides a rigorous probabilistic statistical assessment of the link between observed climate changes and human activities in a way that can inform formal climate risk assessment.”
To do so, they construct a time series model of the temperatures to June 2010 and use the rate of GHG emissions as well as other causal factors such as solar radiation, volcanic emissions and El Niño.
They write, “When the effect of GHGs is removed, bootstrap simulation of the model reveals that there is less than a one in one hundred thousand chance of observing an unbroken sequence of 304 months (our analysis extends to June 2010) with mean surface temperature exceeding the 20th century average.”
They also show that one “would expect a far greater number of short periods of falling global temperatures (as observed since 1998) if climate change was not occurring.” They add, “This approach to assessing probabilities of human influence on global temperature could be transferred to other climate variables and extremes allowing enhanced formal risk assessment of climate change.”
One of the more interesting aspects of this report is that the researchers actually adopt a relatively straightforward time series regression model that is quite prevalent in social science, account for as many variables as they can that would explain climate change outside of human activity (represented by greenhouse gas concentration) and adapt it to determine the chance that the temperature increase would exist without the greenhouse gas concentration increase.
As they explain, “The approach used here allows us to make probabilistic statements about the likelihood of this anomalous warming occurring in the presence or absence of anthropogenic GHG emissions.”
It is worth noting that, according to their data, no one born after February 1985 has lived in a single month where global temperatures fell below the long-term average for that month. According to their analysis, the probability of getting the same run of “warmer-than-average months without the human influence was less than 1 chance in 100,000.”
“We identified periods of declining temperature by using a moving 10-year window (1950 to 1959, 1951 to 1960, 1952 to 1961, etc.) through the entire 60-year record. We identified 11 such short time periods where global temperatures declined,” they write. “Our analysis showed that in the absence of human-caused greenhouse gas emissions, there would have been more than twice as many periods of short-term cooling than are found in the observed data.”
The findings simply tack on more evidence to go with the basic mainstream scientific consensus that global warming is in fact caused by human activity.
In June, the EPA announced that it will mandate power plants in the US to cut carbon emissions by 30% by 2030.
“Earlier this month, hundreds of scientists declared that climate change is no longer a distant threat, it has moved firmly into the present,” the President announced in June. “Last year I put forward America’s first climate action plan, this plan cuts carbon pollution by building a clean energy economy.”
The President argued that, while this is a good start, “for the sake of our children we have to do more. This week, we will.”
“Today about 40% of America’s carbon pollution comes from power plants,” he said. “But right now there are no natural limits to the amount of carbon pollution that existing plants can pump into the air we breathe. None.”
A year ago the President called on the EPA to address this gap in policy by coming up with common sense guidelines, along the lines of efforts already taken by many states, cities and companies.
He said, “These new commonsense guidelines to reduce carbon pollution from power plants were created with feedback from businesses, and state and local governments, and they would build a clean energy economy while reducing carbon pollution.”
Scientists believe that the planet has reach a critical turning point. Right now, nations have set a goal of limiting the warming of the planet to 3.6 degrees Fahrenheit above pre-industrial temperatures. In order for that to happen, global emissions would need to peak by 2020 and then decline.
That does not appear likely.
The Times reports, “Today, emissions are not falling nearly fast enough in the West, and those reductions are being swamped by a rapid rise in the East. Experts say that a global peak in 2020 is exceedingly unlikely, if not impossible — and that will be true even if the United States and other nations manage to keep the pledges they made in 2009.”
They add, “Well into the 2020s, it will still be technically possible to meet the global warming target, but the longer nations put off taking bold action, the more expensive and disruptive it will be to do so once they finally get serious.”
—David M. Greenwald reporting