On Wednesday I spoke with CBC Radio One’s Bob Murphy about NOAA’s State of the Climate in 2015 report. The report is a real eye-opener, painting 2015 as a year of climate records. At least one of those records has already been broken this year.
The report has roughly 470 international authors and editors, and weighs in at 300 pages cover-to-cover. It was published by the American Meteorological Society after peer review.
Let’s have a look at some of the highlights.
The global average surface temperature reached a new high for the second year in a row (Figure 1). 2015 saw temperatures soar to about 1.06°C above preindustrial times. This surpassed 2014 by about 0.15°C, and lops off a good chunk of breathing room left below the 1.5°C limit agreed to in Paris.
The high temperatures in 2015 were associated with strong El Nino conditions in the tropical Pacific which ended this past June. The last time we saw such a strong El Nino was in 1998 – you can see the temperatures spike in Figure 1 – and the lack of a a new record over the next decade fuelled much climate change denialism. The so-called warming “haitus” has ended, and appears to have been just a normal variation around the main trend.
Will 2016 see a new record? This is hard to say. January through June all set new temperature records, making it 14 monthly records in a row. The abatement of El Nino might well end this streak. Time will tell.
Greenhouse gas concentrations continue to rise (Figure 2). Carbon dioxide (CO2) exceeded 400 ppm for the first time ever in 2015, and the annual concentration was a record 399.4 ppm. The increase over 2014 of 3.1 ppm – another new record – is particularly worrisome: It suggests that we continue to make little progress on limiting greenhouse gas emissions.
2016 will almost certainly see a new record. CO2 is a very long-lived greenhouse gas. Anything new we add will remain in the atmosphere for years to come.
Records were also set for methane and nitrous oxide, two other important greenhouse gases.
2015 saw the highest mean sea surface temperature, rising about 0.8°C since 1950. The subsurface ocean heat content was also at a record high.
Sea levels continue to rise with a new record having been set (Figure 3). This may well be exceeded in 2016 given the strong upward trend and continued warmth.
Arctic Sea Ice
Arctic sea ice melts in the summer and refreezes in the winter, with the minimum and maximum extents normally occurring in September and March respectively. The lowest maximum sea ice extent ever was observed in 2015 at 14.54 million km2 (Figure 4). This record has already been broken in 2016.
Global warming is not distributed evenly. In any given year, some places can be relatively warmer or cooler. In 2015, warmer than usual temperatures were observed in Western Canada (Figure 5). It was also drier than normal in Alberta and central BC, leading to 3-4 times more area burned by wildfires than normal. Although Atlantic Canada was slightly cooler than normal in 2015, it was noted that Canada as a whole has warmed 1.6°C over the past 68 years.