The existence of a more than 15-year “pause” in average global surface temperatures has been “settled” but scientists remain split on what it means for the future.
While the level of carbon dioxide in the atmosphere has continued to rise, global surface temperatures have not increased at the same pace, causing speculation over what has happened to the “missing heat”.
Some leading climate scientists claim the missing heat has been absorbed by the world’s oceans and will return with rapid future warming. But new research has found the Earth’s climate is much less sensitive to carbon dioxide than previously thought.
Michael Asten from Monash University’s School of Earth Atmosphere and Environment said that, while opinions on causes differed, the existence of the pause was settled.
“Only activists dare claim the pause in global temperature does not exist,” Professor Asten said.
Australia’s leading public science organisation, CSIRO, has acknowledged the “hiatus” but says its existence does not detract from the urgency of addressing human carbon dioxide emissions.
CSIRO Oceans and Atmosphere Flagship director Helen Cleugh said measurements did show that the rate at which global mean surface temperature had warmed in the past decade was less than in the previous decade. But she said actual temperatures had remained at historic highs. She said that when the entire climate system was considered, the Earth had continued to warm.
“Measurements across the oceans and Earth system as a whole show that warming has continued unabated throughout this period,” Dr Cleugh said.
Climate Council chief executive Amanda McKenzie said her organisation, which includes Will Steffen and Tim Flannery, did not accept there had been a pause.
“No, 2013 marked the 37th year in a row that the yearly global temperature was hotter than the average,” Ms McKenzie said.
“Vested interests have been using the so-called pause to spread doubt and misinformation.”
Federal Environment Minister Greg Hunt said warming of the climate system was “unequivocal”.
“The climate system, which includes the atmosphere, oceans, land and ice, has continued to accumulate heat over the last 18 years,” he said. “The government fully accepts the science.”
Most research has focused on finding the extra heat elsewhere in the climate system. NASA has ruled out an early theory that it was hiding in the deep oceans below 2000m. Other papers have claimed it could be located in the north Pacific and Atlantic oceans.
Another paper says warming of the Southern Ocean has been underestimated in the past.
Dr Asten said he believed the pause in surface temperatures would force scientists to re-examine fundamental assumptions in climate science. “The hiatus demonstrates a disconnect between climate models up to 2013 and physical measurements on our ‘laboratory Earth’,” he said.
IF two of the world’s foremost institutions for climate research can engage in an open and rational discussion about the planet’s obstinate refusal to abide by the strictures of scientific modelling, then it should not be beyond the wit of our national debate.
Britain’s Met Office Hadley Centre bluntly refers to the “recent pause in warming” and recognises that average global surface temperatures have “been relatively flat” since 1998. In the US the National Aeronautics and Space Administration talks about the “global warming hiatus”, declaring that since 1998 the rate of global surface temperature increase has been “one-third of that from 1951 to 2012”. The debate in the science communities of the northern hemisphere is not whether there has been a pause but about the reasons and implications. This is the debate our readers are entitled to and that the nation ought to embrace. Informed scepticism is the essence of scientific endeavour, yet to raise these issues in Australia’s stultifying climate of political correctness and climate dogma too often triggers denunciation or alarmist claptrap. So it is with a breath of fresh air that Monash University’s Michael Asten states the obvious in our pages today. “While opinions on causes differ, existence of the pause is settled,” Professor Asten tells Graham Lloyd. “Only activists dare claim the pause in global temperature does not exist.”
For too long Australian scientists in this field have understood their role to be about fostering public alarm rather than public understanding. Surely Tim Flannery would take back suggestions of permanent drought and dams running dry. Alarmism from the former chief climate commissioner and others of his ilk, along with the dire scenarios presented in their reports, have encouraged governments to act in seemingly irrational ways, such as by investing billions of dollars of scarce public funds in desalination plants that now sit idle. Oblivious to cautionary tales about boys and wolves, their intent has been to concentrate our attention around “dangerous” climate change, “angry” summers and a “critical” decade. To the extent some people now deny any anthropogenic influence on climate, the overblown rhetoric may have played a role; their doomsday visions aren’t reflected in the readily observed reality.
Opinion on the implications of the pause varies. Britain’s Met Office says: “This has prompted speculation that human-induced global warming is no longer happening, or at least will be much smaller than predicted. Others maintain that this is a temporary pause and that temperatures will again rise at rates seen previously.” It has published detailed papers examining how other indicators, such as sea level rises, may still reflect warming and how the pause doesn’t alter the physics or trajectory of long-term warming. Its research suggests likely temperature increases may be 10 per cent below previous forecasts but still substantial. NASA scientists have concluded extra heat is being stored in the oceans rather than being reflected in surface temperatures. Others, such as renowned US climate scientist Judith Curry, provide research that suggests climate sensitivity to carbon dioxide concentrations could be much lower than expected. Her latest research produces “far lower upper limits” than the latest report of the UN’s Intergovernmental Panel on Climate Change. None of this is conclusive but it is where the debate is rightly focused internationally. Quite simply, the alarmists should be taking their own advice — follow the science.
The Weekend Australian has never dismissed the science or the issue. Our view, consistently, has focused on science and evidence. Theory suggests higher concentrations of carbon dioxide will trap more of the sun’s energy in the atmosphere and there is considerable evidence to demonstrate increased emissions have contributed to rising temperatures. Yet there is much about the complex interaction between the atmosphere, oceans, vegetation, volcanic expulsions, sunspots and various forms of pollution that we don’t fully understand. More than 15 years of temperature stability, despite rising emissions, could be a mere blip on long-term climate trends.
Difficult and fascinating as ongoing studies into the causes and trends of climate change are, they are only part of the discussion. Even if we agree on the problem and the extent of the challenge, there will always be debate about the policy response. This is where the work of people like Bjorn Lomborg is so important because it considers the relative costs and benefits of climate action. For many years it has been clear that limiting carbon emissions is a sensible way to mitigate warming or at least ensure against its worst excesses. This newspaper has consistently supported market mechanisms to do this, provided policies are sensibly framed and act in concert with our trading partners. Lack of global action renders a carbon price on our shores an act of economic self-harm and an exercise in environmental futility for now. But debate must continue.
Like the old-timer comparing sea levels at his favourite beach across 50 years, scientific theory must always confront observable reality. This is the ultimate test in climate science that will continue long after we are all gone. So it is frustrating that rather than engage in the discussion, our domestic scientific community has sometimes doubled down on its alarmist language. In response to Lloyd’s inquiries about the pause, the Climate Council’s Amanda McKenzie insists the planet is still warming “strongly” and that “two billion Hiroshima bombs’ worth of heat” have been forced into the atmosphere since 1998. Sigh. Sophistry about the past decade being the warmest also ducks the point; it is not about a decline but whether warming is continuing or pausing at the present high level. The gatekeepers of scientific, media and political debate should not be afraid of a discussion about the facts and their ramifications. And we urge readers to google Britain’s Met Office and Dr Curry’s blog to get to the truth.