By Sarah-Jane O'Connor 21/01/2016 10

It was signposted all year, but North American agencies have confirmed: 2015 was the hottest year since records began in 1880.

NASA and the National Oceanic and Atmospheric Administration (NOAA) analysis showed that global surface air temperatures continued a long trend upward: 15 of the 16 warmest years on record have occurred since 2001.

Globally-averaged temperatures in 2015 surpassed the previous record set in 2014 by 0.13 Celsius. In a statement, NASA and NOAA said the only time the previous record had been beaten by such a margin was 1998.

2014 was the first year global average temperature were 1 degree Celsius or more above the 1880-1899 baseline.

NASA Administrator Charles Bolden said climate change was the “challenge of our generation”.

“Today’s announcement not only underscores how critical NASA’s Earth observation program is, it is a key data point that should make policy makers stand up and take notice – now is the time to act on climate.”

Earth’s average surface temperature has risen about 1 degree Celsius since the late-19th Century, largely driven by increased carbon dioxide and other human-made emissions into the atmosphere.

The long-term change has been visualised by GSFC Scientific Visualization Studio in a video showing a rolling five-year average temperature (orange colors represent temperatures that are warmer than the 1951-80 baseline average, and blues represent temperatures cooler than the baseline).



A warming El Niño was in effect for much of 2015, which Goddard Institute for Space Studies Director Gavin Schmidt said gave the temperatures “an assist”. “But it is the cumulative effect of the long-term trend that has resulted in the record warming that we are seeing.”

New Zealand’s National Institute of Water and Atmospheric Research (Niwa) found 2015 was not a particularly warm year for the country – the 27th warmest since records began – with El Niño dampening things down.

Featured image: Scientific Visualization Studio/Goddard Space Flight Center.

10 Responses to “2015 hottest year on record”

  • I can’t help thinking that this is somehow alarmist propaganda. Some thoughts:

    (1) If the average temperature has risen 1 degree since the 1880-1899 baseline, then how much has the sea level risen since then? At that rate, how many centuries would it take the sea level to rise significantly?

    (2) A global average temperature rise does not directly translate into a sea level rise. A rise in average temperature at the poles does. It is quite possible for the latter to remain constant even if the global average temperature rises.

    (3) Given the billions of years history of the Earth, records starting in 1880 are rather late! Therefore, records don’t tell us much about natural fluctuations/cycles in global temperatures. We therefore don’t really know to what extent any changes are man induced.

    (4) Lastly, it may be that we are getting, rather than a simple warming, more extreme temperatures (hotter summers and colder winters). It would be difficult to predict the consequences of this more complex change. Polar ice would melt more in the summer, but polar seas would freeze more in the winter.

  • A global average temperature rise does not directly translate into a sea level rise. A rise in average temperature at the poles does. It is quite possible for the latter to remain constant even if the global average temperature rises.

    Cough… thermal expansion…cough.

  • As with most other substances, water expands as it is heated (except below 4 Celcius). To be precise, from 4 Celcius and above water expands when it is heated. So Stephen Thorpe’s assertion “A global average temperature rise does not directly translate into a sea level rise” is not correct. Most of the increase in sea level over the last 100 years or so results from thermal expansion of the water in the oceans.

    An increase in temperature at the poles doesn’t necessarily lead to a rise in sea level. When an iceberg melts there is no change in water level, because although ice shrinks when it melts, some of the ice started off above sea level. Sea level rises from polar warming come about when ice that had previously been on land melts, such as in Greenland and Antarctica, both of which have ice caps that are kilometers deep. This is frightening stuff.

    Note that liquid water and ice have relatively unusual expansion/contraction behavior because of the very strong van der Waals forces between water molecules.

  • @Ross Marks

    I find it very hard to believe that thermal expansion makes any significant difference to sea level. Can you pls point to supporting references in the scientific literature for your claims?

    I again make the point that although simplistic global warming may well melt polar (on land) ice caps, a more complex weather pattern involving extremes would result in colder winters whereby a lot of water would freeze. The net result depends on the details.

    • I stand corrected. The thermal expansion of the sea over the last 100 years seems to be closer to one third of the 30cm rise over the past century, not most of it. It is not possible to be precise because the relevant measurements were not made 100 years ago for comparison.

      Ref Wiki “In its Fifth Assessment Report (2013), The IPCC found that recent observations of global average sea level rise at a rate of 3.2 [2.8 to 3.6] mm per year is consistent with the sum of contributions from observed thermal ocean expansion due to rising temperatures (1.1 [0.8 to 1.4] mm per year, glacier melt (0.76 [0.39 to 1.13] mm per year), Greenland ice sheet melt (0.33 [0.25 to 0.41] mm per year), Antarctic ice sheet melt (0.27 [0.16 to 0.38] mm per year), and changes to land water storage (0.38 [0.26 to 0.49] mm per year).”

  • @Steven Thorpe – response/reply to your first post:

    Points 1 and 2 I’m going to wrap this in one response – you appear to assume a linear relationship between temperature and the state of the water molecule where-ever it may be located. If so, you are demonstrably incorrect. Water turns from liquid to solid at a defined temperature. To all intents and purposes there is no incremental change – it happens pretty much in an all or nothing way. Worse, the molecular change from liquid to solid (and vice versa) occurs in such a way that it supports further change in the direction of change – put simply, melting ice melts more ice.

    This therefore leads to a tipping point situation – we will likely see very little change for quite some time and then a sudden, dramatic and non-reversible change.

    Your point three either in error or ignorance overlooks the ability to take records far back in time through care sampling. These samples give the data for long term – even millennial – temperature, humidity and other changes. Direct records may have started in the late 1800’s but a record still exists prior to that point.

    Your point four gives what to me would be a worst case – large fluctuations in conditions. Your proposed conditions imply a huge increase in energy in the global climate system. That would actually be easy to predict outcomes for – there would be significant, widespread disruption in almost all human activity. Storm activity would be stronger (greater temperature differences would drive this) water levels in all bodies of water would rise and fall dramatically with resulting flooding and changes in salinity, winds would be stronger, etc etc. Apocalypse would not be too strong a description.

    I’d say this would be a good reason for taking a precautionary approach immediately.

  • sorry – Stephen. I hate spelling names wrong. Its rude.

    Also, “core” sample not “care” sample.


  • “I’d say this would be a good reason for taking a precautionary approach immediately”

    Precautionary approach = paying carbon tax? Not sure how it helps…