A recently published study has challenged the slowdown in global warming reported by the UN’s Intergovernmental Panel on Climate Change (IPCC) in 2013.
The study produced by the US National Oceanic and Atmospheric Administration (NOAA) and published in the prestigious journal Science on 4th June suggests that the so called “hiatus” in global warming may have been due to artefacts in past datasets and not as many climate change sceptics had hoped a genuine slowdown in the rate of global warming.
The IPCC’s Fifth Assessment Report released in 2013-2014 claimed that the global warming trend between 1998-2012 was “markedly lower” compared to the trend between 1951-2012.
Thomas R. Karl, Director, NOAA’s National Centres for Environmental Information who led the study said: “Our new analysis suggests that the apparent “hiatus” may have been largely the result of limitations in past datasets, and that the rate of warming over the first 15 years of this century has, in fact, been as fast or faster than that seen over the last half of the 20th century.”
The NOAA study used an enhanced global surface temperature (GST) record, which enabled trends to be predicted more accurately. In addition to the GST record NOAA’s calculations also incorporated improved sea surface temperature (SST) and land surface air temperature datasets as well as data from 2013-2014.
An important element of the study was the correction that accounted for differences in data collected from buoys and ships. Historically, SST measurements were captured by ships at sea with a bucket and thermometer. Scientists now tend to capture their SST measurements through instrumentation fitted to ships and buoys.
The difficulty for scientists has always been how to reconcile these different methods of data measurement.
Dr Thomas C. Peterson, principal scientist at NOAA’s National Centres for Environmental Information and one of the study’s authors. “In order to accurately compare ship measurements and buoy measurements over the long-term, they need to be compatible. Scientists have developed a method to correct the difference between ships and buoy measurements, and we are using this in our trend analysis.”
The reaction to the NOAA study has been mixed.
It has been welcomed by bodies such as the UK Met Office who indicated NOAA’s analysis of surface temperature mirrored similar work being done in the UK.
NASA also welcomed the study and indicated they would be incorporating NOAA’s finding into their own datasets.
The Global Warming Policy Foundation, a UK think tank set up by former Chancellor of the Exchequer Nigel Lawson to lobby against action to mitigate climate change were characteristically dismissive of the NOAA study. Their website stated:
“The paper by Karl et al. (2015) published today in Science is an ‘express’ report and not up to the standards of a comprehensive paper. It is a highly speculative and slight paper that produces a statistically marginal result by cherry-picking time intervals, resulting in a global temperature graph that is at odds with all other surface temperature datasets, as well as those compiled via satellite.”
It is clear from the feedback that this study will generate more discussions in the months ahead, especially in the lead up to the UN’s climate change conference (COP21) in Paris at the end of this year. As the old saying goes “all is grist for the mill”.