2012 was among the 10 warmest years on record according to the latest State of the Climate report released this morning by the American Meteorological Society.
The report used dozens of climate indicators to track and identify changes and overall trends in the global climate system. These indicators include greenhouse gas concentrations, temperature of the lower and upper atmosphere, cloud cover, sea surface temperature, sea-level rise, ocean salinity, sea ice extent and snow cover. Each indicator includes thousands of measurements from multiple independent datasets.
A total of 384 authors from 52 countries, including New Zealand, contributed to the peer-reviewed 260-page report.
You can download the full report and a read summary of highlights on the National Oceanic and Atmospheric Administration (NOAA) website.
An interactive map of extreme events in 2012 was released alongside the report, available here.
The SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).
Assoc Prof James Renwick, School of Geography, Environment and Earth Sciences Victoria University of Wellington, was a co-author on the report. He comments:
“This report provides a comprehensive and authoritative record of the state of the global climate, as of the end of 2012. It provides yet more evidence of increasing heat storage in the climate system, when 2012 data are compared to earlier years. The main points to note at a global level are:
1. 2012 was one of the 10 warmest years globally since reliable records began in 1850. No one under the age of 28 has experienced a year with global mean temperature below the 1961-90 average.
2. 2012 saw a new record low end-of-summer Arctic sea ice extent, 3.4 million square kilometres, or about half the average from the 1980s. This value was 18% below the previous record low set in 2007. The main ice loss is in northern summer, strongly increasing the solar heating of the Arctic ocean. [At the same time, Antarctic sea ice is expanding slowly and reached a record maximum in late winter, but this only about 5% above the long-term average.]
3. Sea levels have risen rapidly in the past two years, the rate of rise bouncing back from the dip during the La Niña of 2010/11. Heat content in the top 2000m of the global oceans continues to rise steadily.
4. Greenhouse gas emissions continue to rise, with 2012 setting a new record, surpassing the previous record set in 2011. Atmospheric CO2 concentrations rose about 3ppm in the past year, double the rate of a few decades ago.
“Regionally, the year saw many extreme events around the world, including hurricane Sandy, super-typhoon Bopha, very cold conditions in Europe in late winter (Jan-Feb), extreme drought and heat waves in North America (associated with extensive wildfires in the western USA), drought in Brazil, severe flooding in Pakistan (3rd year in a row) and in west Africa.
“Australia ended the year with a record heat wave in November and more extreme heat and fires early in the new year (January 2013). New Zealand had a near-average year overall in terms of temperature and rainfall. For New Zealand, 2013 has so far been more remarkable than 2012 was, with a severe drought in late summer, a near-record southerly storm in June, and very warm winter temperatures in July and August.”
Dr Jim Salinger, Auckland Climate Scientist, comments:
“The 2012 State of the Climate report shows progressive warming of the planet due to global warming. Features that show we are living in a warmer world include continued increases in global temperatures, diminishing mountain glacier ice masses, record low summer Arctic sea ice extent, increasing melting of the Northern Hemisphere sea ice, and the highest levels of carbon dioixde since 3 to 5 million years ago.
“Warming of surface temperatures has slowed somewhat over the last decade as the excess heat goes into warming up the deep global oceans. More alarmingly the global oceans are becoming increasingly acidic, representing a threat to marine life. In New Zealand the 2012 end of summer snowline survey shows these were 120 metres higher than average in the Southern Alps indicating continuing ice mass loss for the Southern Alps.”
Petra Chappell, climate scientist, NIWA and contributor to the report comments:
“New Zealand climate in 2012 was characterised by more easterly airflows than normal during the first five months of the year and in August, but this changed to more frequent flows from the southwest in June and from September to November.
“There were more frequent highs and northerly winds in July and December, while prolonged easterlies in the early part of the year accounted for the generally dry and sunny conditions in western areas for 2012 as a whole.
“During 2012, extremely heavy snowfall on 6 June set new extreme minimum temperature records for the month and also broke all-time minimum temperature records in some locations.
“A tornado killed three people in Auckland on 6 December, there were eight notable rainfall events, and very warm and humid conditions in late December due to an air mass from ex-Tropical Cyclone Evan.
“There were 82 ‘notable’ extreme events (not including temperature) in 2012, compared with 131 in 2011, and 81 in 2010.
“Mean annual temperatures were near or below average in all regions, with most places within 0.5°C of the long-term (1981-2010) average.
“Some eastern areas were particularly wet in January-March and in August, which significantly increased their annual rainfall totals.”