Detection and Attribution Canadian Temperature Changes to Human Influence

Canada has experienced some of the most rapid warming on earth over the past few decades with a warming rate twice of the global mean temperature. Long-term changes in the observed annual, winter and summer mean temperatures and in the annual coldest and hottest day and night temperatures are compared with simulated responses by multiple climate models under the anthropogenic and natural external forcings. It was found that anthropogenic influence including both greenhouse gases and aerosol and natural external forcing including solar and volcanic activities can be clearly detected and separated from each other in the mean and extreme temperatures at the country scale and in some instance at sub-country scale. Decadal and multi-decadal variability in the climate system including Pacific decadal oscillation (PDO) and North Atlantic oscillation (NAO) may have also played a role on the long-term changes in temperature. It was found that model simulated response matches better with the observed temperature changes if PDO and NAO influence is removed from the original time series.