Dr David Whitehouse
This year is probably going to set a record for global annual average surface temperature. Given this it is inevitable that there will be assertions that the much-debated “pause” in surface temperature is over and that global warming has resumed.
Peter Hannam Environment Editor of the The Sydney Morning Herald is sure that the pause or “hiatus” is over and points to a newly released graph of this year’s temperature. He says, “If there is one chart that might finally put to rest debate of a pause or “hiatus” in global warming, this chart created by the US National Oceanic and Atmospheric Administration has just supplied it.” (Click on image to enlarge.)
The graph shows this year’s monthly temperature plotted against those for the six warmest years on record. According to the NOAA data every month has been the warmest which given the strong El Nino in progress is not that surprising as such El Nino’s generally add 0.1 – 0.2°C to global temperatures. One way of interpreting this graph is that, given the temperature errors – generally plus or minus 0.1°C, the years 2014, 2013, 2010, 2009, 2005, 1998 – are all much the same and that 2015 has been elevated because of a period natural weather event. That’s a long way from saying that the graph puts the debate about the pause to rest. Even Professor Trenberth of the US National Center for Atmospheric Science, has said that the recent warmth is due to weather and not climate. It is chiefly due to the conditions in the Pacific – the El Nino and the so-called ‘blob’ of abnormally warm water – are the cause of 2015 being warmer that 2014.
Far from being over the pause is a hot topic among climate scientists. Some of them say it never existed and were never convinced in the first place, some others say that new data show it was an illusion. The media usually quote them. But there is a large body of research taking place and reported in the peer-reviewed literature that is tackling the reality of the hiatus and seeking explanations for it. In the past few months alone there have been papers discussing the pause and its causes published in the Journal of Geophysical Research, Geophysical Research Letters, Ocean Science, Atmospheric Chemistry and Physics, Earth System Dynamics, Journal of Climate, and Science.
Despite this extensive research taking place Peter Hannam continues in his article with a very out-of-date comment. “For years, climate change sceptics relied on a spike in 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.” This myth has been addressed so many times. The year 1998 and its strong El Nino has nothing to do with the pause. Neither “climate sceptics” nor climate scientists would fall for such an obvious aspect of the data, but it seems journalists still do!
But how does the NOAA data for this year compare to other global surface temperature datasets. Take Nasa Giss for instance which has data up to September. It also suggests that 2015 is going to be the warmest year of the instrumental record. But look carefully at the data and ask two questions. Firstly was each month’s temperature a record and, secondly, was this year warmer than the same month last year? (again with the plus or minus 0.1°C errors in the back of our mind.)
2015 Month Rank Warmer than 2014
Jan 2nd Yes
Feb 2nd Yes
Mar 3rd Yes
Apr 4th No
May 2nd No
Jun Joint 1st Yes
Jul Joint 2nd Yes
Aug 2nd No
Sept 2nd No
This shows a very different picture from the NOAA data. Only one month is the warmest on record and then it tied with 1998. Only five of the nine months were warmer than last year that was also influenced by the El Nino.
What the data is showing us is that over the past 15 years or so there has been little underlying change with El Ninos elevating the temperature a little and La Ninas reducing them. Is what is happening to global annual average surface temperatures all that surprising?