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IEA Greenhouse Gas R&D Programme

67 JG imageNew research led by Australian scientists, and recently published in the journal Nature suggests human impacts had begun to change the climate as back as the 1830’s, earlier than previously expected. Their conclusions were based on natural records of climate variation in the world's oceans and continents, including those found in corals, ice cores, tree rings and the changing chemistry of stalagmites in caves.

Global warmingInterestingly, the change comes sooner to northern climes, with regions such as Australasia not experiencing a clear warming signal until the early 1900’s. See chart from the Nature paper that shows the onset times of warming depicted by the vertical bar in each region's plot

One implication is that the paper shows an extra "couple of tenths of one degree" must be added to what are generally taken to be the baselines of warming since key instrumental records start from the 1880s.

Carbon dioxide concentrations increased from about 1765 with the Industrial Revolution, whilst methane concentrations began ticking hjosirer from about 1700 as agriculture became more intensive.

One other point noted is that in the models and observations there is good agreement for the northern hemisphere and tropical oceans, but this is not so for the southern hemisphere, and thus warrants further research.

The researchers conclude that the oceans had been doing humans a big favour by absorbing most of the extra heat being trapped by greenhouse gases – more than 90 per cent – but much is still to be learnt about whether this phenomenon can continue. The question they raise is "when is this heat going to be released, and what are the thresholds for changing the climate?"