17th June 2015
NASA: 2015 is the hottest year on record (so far)
NASA has just released its latest update for GISTEMP – one of the most widely-cited datasets for the measuring of global temperatures. This shows that the first five months of this year were the hottest five-month period on record by a considerable margin. So far, 2015 has been 0.77°C (1.4°F) warmer than the 1951-1980 baseline. This is compared to 0.68°C (1.2°F) set during 2014, the previous record year.
These record high temperatures have occurred even before a substantial El Niño has yet to take full effect. Taking the pre-industrial temperature as the baseline (instead of 1951-1980) and projecting a future trend, the world is on course for a 1°C (1.8°F) rise by the early 2020s. One degree of warming might not sound like much, but the energy required to heat the entire surface and lower atmosphere of a planet is huge – equivalent to four Hiroshima atomic bombs detonating every second. That heat is being trapped by greenhouse gases, as shown by simple laboratory experiments and theorised as far back as the mid-19th century.
If global warming is to be kept below 2°C this century, then over 80% of coal, 50% of gas and 30% of oil reserves are "unburnable", according to a recent study published in Nature. This means that drilling in the Arctic Circle should be prohibited, since it contains a large fraction of the world's undiscovered oil and gas. Despite this scientific conclusion and the long-term risks, a number of nations including Canada, Russia and the US are racing to claim the available resources.
GISTEMP is based on publicly available data from 6,300 meteorological stations around the world; from ship-based and satellite observations of sea surface temperatures; and from Antarctic research stations. These three data sets are combined and adjusted to account for breaks in station records, the effects of urban heating, and the distribution of stations across the landscape.