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Climate scientists see 'tipping point' ahead

'The Day After Tomorrow' may come the day after tomorrow

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The authors' suggestion? Not what you think

The paper argues that it's humans who are currently the prime biosphere stressors. The authors note, for example, that the atmospheric CO2 concentrations that are now about 35 per cent higher than pre-industrial levels – hitting 400ppm over the arctic this spring – have caused the earth's oceans to become more acidic. Increased CO2, the paper contends, contributes to "a higher rate of global warming than occurred at the last global-scale state shift," and will result in the mean global temperature by 2070 or earlier being "higher than it has been since the human species evolved."

Also, plants are migrating due to climate disruption. "Modelling suggests that for ~30 per cent of Earth," the authors write, "the speed at which plant species will have to migrate to keep pace with projected climate change is greater than their dispersal rate when Earth last shifted from a glacial to an interglacial climate, and that dispersal will be thwarted by highly fragmented landscapes."

Among other anthropogenic biosperical changes, the paper cites ocean "dead zones" and nutrient-cycle disruptions due to pollutants from agricultural run-off and urban areas.

With all this Sturm und Drang, you could understandably imagine that the central thesis of "Approaching a state shift in Earth's biosphere" might be an impassioned plea for humankind to put the brakes on anthopogenic climate disruption. You'd be wrong.

What Barnosky and his international team are arguing for is an increased focus by the scientific community on developing processes and procedures for analyzing the many and varied factors that might push the biosphere into a global-scale state change. "The plausibility of a planetary-scale 'tipping point'," they argue, "highlights the need to improve biological forecasting by detecting early warning signs of critical transitions on global as well as local scales, and by detecting feedbacks that promote such transitions."

Recent research in state-shift theory, they argue, shows that mathematical risk-assessment models can to be developed to illuminate various and sundry data sets and divine what they can tell us about the approaches of biospherical systems towards "tipping points".

More work also needs to be done, they argue, to understand how global changes affect local changes – and, of course, vice versa. This is a particularlty sticky problem, they admit, seeing as how it is fiendishly difficult to define what might be considered an "unusual" change in a system, "because biological systems are dynamic and shifting baselines have given rise to many different definitions of 'normal', each of which can be specified as unusual within a given temporal context."

And then there's the complexities of what they refer to as "scale-jumping" effects – that is, when one set of biospherical changes affects another in unforseen ways, such as, for example, how changes in rainfall amounts can lead to changes in plant pollination cycles.

"These 'scale-jumping' effects, and the mechanisms that drive them," they write, "have become apparent only in hindsight, but even so they take on critical importance in revealing interaction effects that can now be incorporated into the next generation of biological forecasts."

The problem is an immense one, seeing as how the global ecosystem is composed of a myrid of interlocking smaller-scale ecosystems, each of which interact in complex dances of cause and effect – and because of that interaction, state shifts in small-scale systems can propagate to lead to a state shift in the entire system.

Although the paper's main focus is on the need for better tools to monitor, predict, and perhaps defer a negative biospherical tipping point, the authors are intellectually honest enough to put their cards on the table and provide their own recommendations as to what could be done now to lower the probability that such a tipping point – aka "rapid and unpredictable transformations within a few human generations" – might occur:

  • reducing world population,
  • reducing per-capita resource use,
  • reducing the role of fossil fuels,
  • improving energy efficiency,
  • increasing the efficiency of food production and distribution,
  • "and enhancing efforts to manage as reservoirs of biodiversity and ecosystem services, both in the terrestrial and marine realms, the parts of Earth's surface that are not already dominated by humans."

Of course, those who dismiss climate disruption as a "hoax" perpetrated by grant-seeking scientists – or, more kindly, as simply an unfounded set of errors in measurement, analysis, or judgment – will see little reason to undertake what Barnosky and his team refer to as these "admittedly huge tasks."

But even if the science underpinning climate change isn't nailed down as tight as a drum – as little emerging science is – and although reasonable observers can have reasonable differences of opinion, it's difficult to mount a plausible argument against developing mathematical models that could help predict a negative biospherical tipping point, and convincingly illuminate steps that might be taken to avoid it.

It's equally difficult to argue that we puny but ubiquitous humans have had little effect on our planet. As the paper's authors note, "Humans have already changed the biosphere substantially, so much so that some argue for recognizing the time in which we live as a new geologic epoch, the Anthropocene." ®

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