Australia was home to some of the most extreme temperature shifts in 2013, according to the United Nations' authoritative voice on weather, climate and water, the World Meteorological Organisation (WMO).
The year 2013 is currently on course to be among the top ten warmest years since modern records began in 1850, the WMO said in a statement issued at the UN climate change conference in Warsaw, Poland.
The first nine months, January to September, tied with 2003 as the seventh warmest such period on record, with a global land and ocean surface temperature of about 0.48°C (0.86°F) above the 1961–1990 average.
WMO’s provisional annual statement on the Status of the Global Climate 2013 provides a snapshot of regional and national temperatures and was released overnight to inform negotiators at the UN conference.
In contrast with 2012, when the United States, in particular, observed record high annual temperatures, the warmth in 2013 was most extreme in Australia.
“Temperatures so far this year are about the same as the average during 2001-2010, which was the warmest decade on record,”WMO Secretary-General Michel Jarraud said.
"All of the warmest years have been since 1998 and this year once again continues the underlying, long-term trend. The coldest years now are warmer than the hottest years before 1998.
“Atmospheric concentrations of carbon dioxide and other greenhouse gases reached new highs in 2012, and we expect them to reach unprecedented levels yet again in 2013. This means that we are committed to a warmer future."
“Surface temperatures are only part of the wider picture of our changing climate. The impact on our water cycle is already becoming apparent – as manifested by droughts, floods and extreme precipitation.”
The provisional WMO statement confirms that global sea level reached a new record high. Sea level has been rising at an average rate of about 3.2 milimeters per year (mm/yr), with inter-annual variability, since altimeter satellite measurements began in 1993.
This is close to the observed rate of about 3 mm/yr of the most recent decade of 2001−2010 and double the observed 20th century trend of 1.6 mm/yr.
More than 90 per cent of the extra heat generated from greenhouse gas is absorbed by the oceans.
During the first nine months of 2013, most of the world’s land areas had above-average temperatures, most notably in Australia, which recorded its all-time warmest 12-month period from November 2012 to October 2013.
The amount of greenhouse gases in the atmosphere reached a new record high in 2012.
The WMO's annual Greenhouse Gas Bulletin shows that between 1990 and 2012 there was a 32 per cent increase in radiative forcing – the warming effect on our climate – because of carbon dioxide (CO2) and other heat-trapping long-lived gases such as methane and nitrous oxide.
Carbon dioxide, mainly from fossil fuel-related emissions, accounted for 80 per cent of this increase. The atmospheric increase of CO2 from 2011 to 2012 was higher than its average growth rate over the 10 years.
Since the start of the industrial era in 1750, the global average concentration of CO2 in the atmosphere has increased by 41 per cent, methane by 160 per cent and nitrous oxide by 20 per cent.
“The observations from WMO’s extensive Global Atmosphere Watch network highlight yet again how heat-trapping gases from human activities have upset the natural balance of our atmosphere and are a major contribution to climate change," Jarraud said.
“The Intergovernmental Panel on Climate Change (IPCC) in its recent 5th Assessment Report stressed that atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years.
“As a result of this, our climate is changing, our weather is more extreme, ice sheets and glaciers are melting and sea levels are rising."
According to the IPCC, global average temperatures could be 4.6 degrees higher by the end of the century if action is not taken immediately to reduce greenhouse gas emissions.
"This would have devastating consequences which is why we need to act now, time is not on our side," Jarraud said.
The Bulletin said the amount of CO2 in the atmosphere reached 393.1 parts per million in 2012, or 141 per cent of the pre-industrial level of 278 parts per million.
Jarraud said the amount of CO2 in the atmosphere increased 2.2 parts per million from 2011 to 2012, which is above the average 2.02 parts per million per year for the past 10 years, showing an accelerating trend.
Monthly observed concentrations of CO2 in the atmosphere exceeded the symbolic 400 parts per million threshhold at several Global Atmosphere Watch stations in the Arctic during 2012. During 2013 hourly and daily concentrations passed this threshold in other parts of the world,.
At the current rate of increase, the global annual average CO2 concentration is set to cross the 400 parts per million threshold in 2015 or 2016.
Methane is the second most important long-lived greenhouse gas. Approximately 40 per cent of methane is emitted into the atmosphere by natural sources (e.g., wetlands and termites), and about 60 per cent comes from human activities like cattle breeding, rice agriculture, fossil fuel exploitation, landfills and biomass burning.
Atmospheric methane reached a new high of about 1819 parts per billion (ppb) in 2012, or 260 per cent of the pre-industrial level, due to increased emissions from anthropogenic sources. Since 2007, atmospheric methane has been increasing again after a temporary period of levelling-off.
The concentration of nitrous oxide in 2012 was about 325.1 parts per billion, which is 0.9 parts per billion above the previous year.
The total radiative forcing by all long-lived greenhouse gases in 2012 corresponds to equivalent CO2 concentration of 475.6 parts per million, compared to 473.0 parts per million in 2011.
Other long-lived greenhouse gases include ozone-depleting chlorofluorocarbons (CFCs), as well as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) which are increasing at relatively rapid rates.