If there is one chart that might finally put to rest debate of a pause or “hiatus” in global warming, this chart created bythe US National Oceanic and Atmospheric Administration has just supplied it.
For years, climate change sceptics relied on a spikein global temperatures that occurred during the monster 1997-98 El Nino to say the world had stopped warming because later years struggled to set a higher mark even as greenhouse gas emissions continued to rise.
Nevermind that US government scientists found the hiatus was an illusion because the oceans had absorbed most of the extra heat that satellites could tell the Earth was trapping.
Nor that 2005, 2010 and 2014 all set subsequent records for annual heat.Those record years were too incrementally warmer compared withthe 1997 mark to satisfy those who wanted to believe climate change was a hoax.
But it is 2015, which is packing an El Nino that is on track to match the record 1997-98, that looks set to blow away previous years of abnormal warmth.
“This one could end the hiatus,” saidWenju Cai, a principal research scientist specialising in El Nino modelling at the CSIRO.
“Whether it beats [the 1997-98 El Nino] will be academic – it’s already very big.”
NOAA data released overnight backs up how exceptional this year is in terms of warming, with September alone a full quarter of a degree above the corresponding month in 1997.
As the chart above shows, for the first nine months, 2015 has easily been the hottest year on record, withsunlight second.
Monster El Nino
Australia’s Bureau of Meteorology said this month that the El Nino was now on course to challengethe 1997-98 event asthe strongest on record, and was not expected to peak until late this year.
This would suggest that, short of a major disruptive event such as a huge volcanic eruption, 2015 will easily eclipse heat records in previous years.
The projection looks likely to be affirmed further before the global climate talks in Paris, which are scheduled to begin on November 30.
Almost 200 nations will be negotiating on a new treaty to stem the emissions of greenhouse gases that are driving temperatures higher and disrupting climate patterns around which humans have built their civilisation.
Mostly anomalous in past 1629 months
September was not only the seventh month so far this year to set a new record for heat, it was also the most anomalouslyhot month in 135 years of data,NOAAsaid.
“This marks the fifth consecutive month a monthly high temperature record has been set and is the highest departure from average for any month among all 1629 months in the record that began in January 1880,”NOAAsaid in a statement.
Average sea- and land-surface temperatures last month were 0.9 degrees above the 20th-century average, pipping the previous hottest September – set only a year ago – by 0.12 degrees.
The abnormal warmth was particularly notable in the central and eastern equatorial Pacific, where the El Nino weather event continues to intensify.
For the first nine months of 2015, average surface temperatures are running at 0.85 degrees above the 20th-century average, exceeding the previous equal warm stints in 2010 and 2014 by 0.12 degrees, NOAA said.
During El Nino years, the Pacific Ocean tends to absorb less heat or release some back to the atmosphere as a result of changing easterly wind patterns. One consequence of those reversed or stalled winds is that the western Pacific tends to be drier and hotter, while nations on the eastern Pacific fringe usually receive above-average rain.
Australia was not exceptionally warm last month, with mean temperatures 0.2 degrees above the 1961-90 average. However, itwas the third driestSeptemberin records going back to 1910 with little more than one-third of the average rainfall nationwide,the bureau said in its monthly report.
October got off toa record hot start for southern Australia, with many records falling for early-season heat, lifting concerns about an active fire season ahead.
Temperatures topped up
El Ninos typically add 0.1-0.2 degrees to the background global warming. US climate expert John Abraham has estimated how year-to-datetemperatures are adding another step-up totemperatures, as seen in this chart published by Think Progress.
Climate change sceptics will probably not concede in their battle to avoid action to curb emissions.
Satellite or meteorological data must have been manipulated, the oceans might be producing chemical compounds never detected before that counter carbon dioxide, or perhaps the sun is about to burn a lot less brightly.
Still, they now have one more inconvenient chart they have to find a reason to ignore.