By Tim Radford / Climate News Network

    Changes in cherry blossom flowering times are indicators of climate shift. (Lovisa Lagerqvist via Flickr)

This Creative Commons-licensed piece first appeared at Climate News Network.

LONDON — Climate change may have begun more than 25 years ago. At around the time that global warming and the spectre of climate change first emerged as a geopolitical challenge for future generations, it had already commenced, according to new research.

As world leaders gather in Paris for COP21, the UN summit seeking to get a global agreement on responses to climate change, British oceanographers and colleagues from around the world have identified a “major change in the Earth’s biophysical systems” in the late 1980s.

They looked back into recent climate history, and now say that the change can be attributed to “rapid global warming from anthropogenic plus natural forcing.”

Climate scientists have been warning for decades that the build-up of greenhouse gases in the atmosphere, as a result of the human combustion of fossil fuels, will at some point tip stable climate zones into new regimes — a shift defined by the researchers as an “abrupt, substantial and persistent” change.

Most climate scientists expect such change to happen in the next few decades, but this new study seems to declare that it has already started to happen.

Cause and effect

The scientists report in Global Change Biology journal that they have identified a worldwide pattern of change, centred around 1987, that was seemingly associated with the eruption of Mexico’s El Chichón volcano in 1982.

Analyses such as these are complex. No single weather event can be taken as significant, while cause and effect also are not easily linked.

But the researchers are sure they have found a significant pattern emerging from a huge range of records — from cherry blossom times in Japan, Washington DC and Switzerland to grape ripening dates in Germany, and from the arrival of the migrant sand martins in the UK to the duration of wildfires in the western US.

“We demonstrate, based on 72 long time series, that a major change took place in the world centred on 1987 that involved a step change and move on to a new regime in a wide range of Earth systems,” says the study’s lead author, Philip “Chris” Reid, professor of oceanography at Plymouth University’s Marine Institute in the UK.

“A major change took place in the world
centred on 1987 that [led to] a new regime
in a wide range of Earth systems.”

“Our work contradicts the perceived view that major volcanic eruptions just lead to a cooling of the world. In the case of a regime shift, it looks as if global warming has reached a tipping point where the cooling that follows such eruptions rebounds with a rapid rise in temperature in a very short time.

“The speed of this change has a pronounced effect on many biological, physical and chemical systems throughout the world, but is especially evident in the Northern temperate zone and the Arctic.”

Any research that “contradicts a perceived view” is likely to be examined, challenged and countered by other climate scientists. One study will not settle the argument, but observers with long memories will recognise that this hindsight evidence for climate regime shift coincides with the moment that climate change emerged as a political subject in 1988.

During a prolonged drought and devastating heatwave that summer in the US and Canada, the then NASA scientist James Hansen warned a US senate committee: “It’s time to stop waffling so much and say the evidence is pretty strong that the greenhouse effect is here.”

Marked decline

Professor Reid and his colleagues have now detected a marked decline in the growth rate of carbon dioxide after the regime shift, coinciding with the growth of new vegetation on land and sea that had once been under ice and snow.

They found that the annual timing of the regime shift moved around the world from west to east, starting with South America in 1984, North America a year later, the north Atlantic in 1986, Europe in 1987, and Asia in 1988.

Data from the time series embraces a huge range of systematically-measured events, such as the temperature of rivers in Switzerland, the mass of phytoplankton in the North Sea, and the Japan Sea tuna catch.

During this period, the winter river flow into the Baltic increased by 60%, and the average duration of wildfires in the western US increased fourfold. The scientists estimate that the shift in the 1980s was the largest in a thousand years.

The researchers conclude that the shift they perceive will affect how the seas, forests and wetlands soak up carbon from the atmosphere, a key factor in continuing climate change.

“The wide range of changes associated with the 1980s regime shift supports a threshold thesis that moved the whole global system into a new, rapidly warming state, with compounding consequences,” they say.

Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.

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