A major international climate study has confirmed that the past decade was the warmest on record and that the Earth has been growing warmer over the last 50 years.
The 2009 State of the Climate report released today by the US National Climatic Data Centre (NCDC) drew on data from many measurable climate indicators that all pointed to the same finding: the scientific evidence that our world is warming is unmistakable.
Dr Lisa Alexander, a senior lecturer in the UNSW Climate Change Research Centre, was one of the lead authors of the study, as editor and author of Chapter 2 - Global Climate.
"This is NOAA's most comprehensive statement of the global climate to date," says Dr Alexander. "It brought together over 300 authors from 48 countries. In the chapter on global climate in which I was involved there were 61 authors, so it was a difficult task to organise the summary and ensure that everything was done comprehensively and consistently.
"The main take home message from the report is that average surface temperature estimates for the globe in 2009 marked the end of the warmest decade in the instrumental record - that is, since about 1870.
"Each of the last three decades has been progressively warmer than all earlier decades. This is irrespective of which of the multiple independent data sources that are used to calculate global surface temperature.
"In total, 37 climate indicators were analysed in the report. They included, for example, surface temperature over the land and oceans, temperatures and humidity in the atmosphere and the size and extent of glaciers. They all point to a climate that is responding to a warming world and the effects of increases in global concentrations of greenhouse gases.
"Last year was one of the top 10 warmest years globally and 2009 also ended Australia's warmest decade since records began in 1910 - 0.48 deg C above the 1961-1990 average.
"Preliminary data indicate a high probability as well that 2009 will be the 19th consecutive year that glaciers have lost mass. Greenhouse gas concentrations continued to rise in 2009, with CO2 increasing at a rate above the 1978 to 2008 average.
"Some new satellite technologies for deriving weather and climate parameters have been introduced into the report for the first time, providing the exciting potential for further independent estimates of global surface temperature for example."