Attempts to modify the climate through reducing CO2 emissions may turn out to be futile.
In a press conference last week, UN Secretary-General Ban-Ki Moon stated: “Action on climate change is urgent. The more we delay, the more we will pay in lives and in money.” The recently appointed UN Messenger of Peace, Leonardo DiCaprio, stated “The debate is over. Climate change is happening now.”
These statements reflect a misunderstanding of the state of climate science and the extent to which we can blame adverse consequences such as extreme weather events on human-caused climate change. The climate has always changed and will continue to change. Humans are adding carbon dioxide to the atmosphere, and carbon dioxide and other greenhouse gases have a warming effect on the climate.
However, there is enduring uncertainty beyond these basic issues, and the most consequential aspects of climate science are the subject of vigorous scientific debate: whether the warming since 1950 has been dominated by human causes, and how the climate will evolve in the 21st century due to both natural and human causes. Societal uncertainties further cloud the issues as to whether warming is “dangerous” and whether we can afford to radically reduce carbon dioxide emissions.
At the heart of the recent scientific debate on climate change is the “pause” or “hiatus” in global warming – the period since 1998 during which global average surface temperatures have not increased. This observed warming hiatus contrasts with the expectation from the 2007 IPCC Fourth Assessment Report that warming would proceed at a rate of 0.2oC/per decade in the early decades of the 21st century. The warming hiatus raises serious questions as to whether the climate model projections of the 21st century have much utility for decision making, given uncertainties in climate sensitivity to carbon dioxide, future volcanic eruptions and solar activity, and the multi-decadal and century-scale oscillations in ocean circulation patterns.
A key argument in favour of emission reductions is concern over the accelerating cost of weather disasters. The accelerating cost is associated with increasing population and wealth in vulnerable regions, and not with any increase in extreme weather events, let alone any increase that can be attributed to human-caused climate change.
The IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation found little evidence that supports an increase in extreme weather events that can be attributed to humans. There seems to be a collective “weather amnesia,” where the more extreme
weather of the 1930’s and 1950’s seems to have been forgotten.
Climate science is no more “settled” than anthropogenic global warming is a “hoax.” I am concerned that the climate change problem and its solution have been vastly oversimplified. Deep uncertainty beyond the basics is endemic to the climate change problem, which is arguably characterized as a “wicked mess.” A “wicked” problem is complex with dimensions that are difficult to define and changing with time. A “mess” is characterized by the complexity of interrelated issues, with suboptimal solutions that create additional problems.