The Intergovernmental Panel on Climate Change (IPCC), the global community’s scientific authority on climate matters, will release its Fifth Assessment Report (AR5) next month. A leaked draft version has been appearing on websites for almost a year, and capturing headlines in the media.
What is the new IPCC report saying?
The Fourth Assessment Report (AR4) released in 2007 concluded that warming of the climate system is unequivocal. Further support is given for this conclusion in the AR5 through new observations, longer data sets, and more paleo-climate information. Confidence is stronger that many changes in the climate system are significant, unusual or unprecedented. Widespread warming is observed across the surface of the Earth, as well as in the upper ocean. Each of the last three decades has been significantly warmer than all preceding decades since 1850.
According to the new report, there is now “incontrovertible evidence” that atmospheric concentrations of greenhouse gases have increased in the last 200 years, causing the average temperature of earth’s atmosphere and oceans to rise. So much evidence now exists that the draft says scientists are “virtually certain” human activity is the main driver of climate change, which means they are at least 99 per cent sure. In AR4, the figure was lower, 90 per cent, so scientific certainty has increased.
The most pessimistic projections for global temperature rise, although they may be the most realistic, is between 3 and 5 degrees Celsius by 2100. Sea levels are projected to rise by between 29 and 82 centimeters by the end of the century.
What do the new IPCC projections mean for Prince Edward Island?
The new IPCC global climate model projections show a future climate for PEI in the 2050s that is warmer 2-3 degrees Celsius and wetter by 5-9% in precipitation (that is rainfall and snow), this means hotter and a bit wetter. This is a little different from what my own research on climate has shown for PEI over the past 30 years. PEI has definitely gotten warmer and drier according to climate observations. But we don’t have to believe the scientific instruments alone, just ask any farmer or fisherman who is out in the weather every day and they’ll tell you that the climate is changing towards warmer and drier seasons.
The impacts from this anticipated warmer and wetter climate will be varied, resulting in both positive and negative impacts. The positive effects would be longer growing seasons so farmers can expect more and varied crops from their land; more warm water fish catches such as lobster; less costs for snow removal; more beautiful days for playing golf and being outside. The negative effects would be more insects, pests and diseases for our crops; more invasive fish species in our water; more days that we wish we had air conditioning. Probably most frightening for PEI is an increase in coastal erosion through higher sea levels and increased storm surges. PEI is already seeing major coastal erosion all across the Island, sometimes in the meters per year, and we scientists expect that damage to increase under climate change.
Why the change? From very likely to virtually certain that humans are the cause of the warming?
New evidence, gathered through climate research and monitoring activities is now available. The IPCC has a scale called the “Likelihood scale” which connects language of certainty to an amount of probability, or likelihood that an event will occur. The IPCC determines uncertainty through expert judgement – they examine the results from climate research and monitoring activities, and then weigh the evidence. Computers are getting faster and stronger. They are able to integrate more information and data in making projections of future climate change so scientists have more and more confidence in the overall results.
Remember that this leaked draft IPCC document remains to be edited and approved through more meetings of scientists. But the main message is there – the climate is getting warmer and scientists are more confident that it will continue to do so.