The Rate and Impact of Climate Change

by Peter Dixon

Recent information should jolt us out of our dream-time state that climate change is only a slow process and that its impact is probably not within our lifetime or even within our children or grandchildren’s lifetime. New evidence by credible scientific institutions reveal that periods of gradual change in earth’s past were punctuated by episodes of abrupt climate change.

The US National Academy of Sciences (NAS) Committee’s Abrupt Climate Change, Inevitable Surprises report said that human activities could trigger abrupt climate change.

It also stated, “Roughly half the north Atlan­tic warming since the last ice age was achieved in only a decade and it was accompanied by significant climatic changes across most of the globe.” Warming at the end of the Younger Dryas (a cooling period) occurred in one especially large step of about 8 degrees Celsius in about 10 years ac­cording to the NAS.

Furthermore “Greenhouse warm­ing and other human alterations of the earth system may increase the possi­bility of large, abrupt, and unwelcome regional or global climatic events,” NAS said.

NAS has called this reorientation in the thinking of scientists a veri­table “paradigm shift” and says “It has been well established by research over the last decade, but this new thinking is little known and scarcely appreciated in the wider community of natural and social scientists and policymakers.”

The United Nations Intergov­ernmental Panel on Climate Change (IPCC) report Summary for Policy Makers said a “Sustained rapid cli­mate change could shift the competi­tive balance among species and even lead to forest dieback, altering the ter­restrial uptake and release of carbon” and that “There is new and stronger evidence that most of the warming observed over the last 50 years is at­tributable to human activities.”

Scientists on the IPCC empha­sized in another report, Rapid Non-linear Climate Change, that “Seem­ingly small disturbances can create large and rapid responses when the climate system is near …threshold conditions.” They raised the issue of “dangerous anthropogenic [human in­fluence] interference with the climate system.”

The US National Science Founda­tion (NSF) led the Greenland Ice Sheet Project 2 (GPS 2) in 1993 – involving 25 universities – to tease-out past climate scenarios from old trapped air gas bubbles and dust captured in ice-cores reaching a depth of 3000 metres (almost 2 miles). By analyzing 110,000 years of the Earth’s climate history, the research revealed that swift change occurred many times in the past, from thousands of years to centuries to as little as a decade.

In recent times, the Helm and Il­lecillewaet Glaciers in British Colum­bia retreated 1,100 metres in the last 100 years and other glaciers are losing significant volumes. Also, the central Arctic sea-ice thinned by about 40 percent from 1993 to 1997.

Glaciers are highly responsive to rapid climate change and they are receding rapidly in many areas.

The GPS 2 and its nearby coun­terpart the European Greenland Ice Core Project compared data, con­cluding that the well-dated ice-core records shift the commonly held view that climate variability only operates on a slow time scale. According to the National Research Council this dis­covery is supported by palaeoclimatic records from marine sediment cores and tree rings that showed periodic episodes when the climate changed rapidly within a few years.

The US Atmospheric Palaeocli­matology Program of the National Geophysical Data Centre came to the same conclusion: rapid step-like shifts in climate variability over decades or less, as well as climate extremes that persist for decades, occurred repeat­edly in recent earth history.

It is clear that there were abrupt climate changes in the past and they will very likely be repeated in the future. It reinforces our concerns about the human influence on climate change due to greenhouse gas emis­sions. The National Research Council of NAS said, “Current trends along with forecasts for the next century indicate that the climate averages and variabilities likely will reach levels not seen in instrumen­tal records or in recent geological history.” The hazards are disruptions to ecosystems, economic systems, and certainly to the safety of humans living in vulnerable loca­tions.

Could greenhouse gas emissions by humans be the pressure point that flips the switch to abrupt climate change? Nature has many examples where the unusual ap­plication of force causes unexpected behaviour.

Is abrupt climate change a pos­sibility within the lifetimes of our children and our grandchildren, per­haps even our own? Policy makers in governments and industry should take note and act accordingly.

***

[From WS March/April 2004]

5 Issues/yr — $25 print; $15 digital