The signs of global warming are hitting us over the head today — if you'll remember, the fire and drought-ridden summer of 2015 was the also hottest in recorded history — but how long has our planet actually been feeling the heat? In parts of the tropics, anthropogenic climate change has been tinkering with the thermometer since the 1940s.
That's the surprising conclusion of a new modelling study published today in Environmental Research Letters. Running 23 global climate simulations that combine historical trends (beginning in 1860) with future emissions scenarios, researchers at the University of South Wales estimated when the very first fingerprints of climate warming — extreme temperatures and shifts in the mean annual temperature — would have become measurable across the world, had we been paying any attention. Near the equator, the writing was on the wall decades before the concept of anthropogenic climate change had been realised.
"Remarkably our research shows that you could already see clear signs of global warming in the tropics by the 1960s but in parts of Australia, South East Asia and Africa it was visible as early as the 1940s," said lead study author Andrew King in a statement. (That's decades before the the fore-thinking researchers at Exxon discovered global warming!)
Climate change is hitting high latitude ecosystems the hardest — the Arctic, for instance, is warming twice as fast as the world at large. For that reason — and the fact that most big research universities are located in countries with seasons — what's happening in the tropics has been largely ignored. But as the new study shows, tropical ecosystems may offer an even better long-term thermometer. Lacking a distinct summer and winter, the tropics have a much narrower distribution of temperatures year-round, which makes it easier, statistically speaking, to spot small deviations and outliers years.
Modelled time period at which climate change became or will become detectable in a variety of indicators, including (a) and (b) mean surface air temperature, (c) and (d) highest daily maximum temperature, (e) and (f) lowest daily minimum temperature, (g) and (h) total precipitation, and (i), (j) maximum 1-d precipitation. Image Credit: University of New South Wales
And while the tropics are experiencing smaller levels of warming than, say, boreal forests, climate change stands to wreak even more ecological havoc around the equator. Remember, tropical flora and fauna are adapted to a pretty narrow range of (already high) temperatures. What happens when you take the hottest forests in the world and crank up the heat even more? We're not sure yet — scientists are currently building the first tropical climate warming experiments are currently to address that very question.
But given that tropical forests sequester more carbon than temperate and boreal forests combined, I'm gonna go out on a limb here and suggest this is one global experiment we'd be wise to halt.
[Read the full scientific paper at Environmental Research Letters]
Top image: Aerial view of the Amazon rainforest in Brazil, via Wikimedia