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At a climate tipping point.

Andrew Glikson.

global warming graphic based on word frequency. woodleywonderworks. flickr cc.

According to Hans Joachim Schellnhuber, chief climate advisor to the European Union, “We’re simply talking about the very life support system of this planet”. As fascism and the horror of murderous hate crimes are spreading around the world, governments are presiding over runaway climate change, leading toward a mass extinction of species, costing the lives of billions and the demise of much of nature, while children are protesting the betrayal of their future.

More than 30 years since Professor James Hansen, then NASA’s chief climate scientist, presented a stern warning to the US Senate regarding the existential risk posed by global warming, the consequences are upon us of the ignorance, criminal denial, and pro-carbon ideology promoted by vested interests and their accomplices among the political classes and in the media, as the climate system is shifting into a dangerous uncharted territory. While the Earth as a whole continues to heat, transient temperature polarities between warming land masses, and Arctic-derived cold air masses lead to extreme weather events.

Evidence based on early climates and on current global warming requires revision of the mostly-linear International Panel of Climate Change (IPCC) climate change trajectories proposed for the 21st to 23rd centuries. The polar ice sheets, acting as the thermostats of the climate controlling the current mean Earth surface temperature of 15oCelsius, are melting at an accelerated rate.

Polar temperatures have been rising at twice the rate of lower latitude zones, weakening the jet stream and the Arctic boundary, which is becoming increasingly undulated. This allows cold air masses to breach the boundary as they move southward, as happened recently in North America and Europe, while warm air masses migrate northward. As the large ice sheets are melting, large pools of cold ice melt water are forming in the North Atlantic Ocean south and east of Greenland (Rahmstorf et al 2015). The AMOC (Atlantic Meridional Ocean Circulation) is slowing down, and the probability of future transient freeze event/s (stadials) lasting a few decades or longer (Hansen et al 2016) is increasing. The juxtaposition of polar-derived freezing fronts and tropics-derived warm air masses leads to a rise in extreme weather events.

Arctic air temperatures for 2014-2018 have exceeded all previous records since 1900. According to NOAA, Arctic warming has led to a loss of 95 percent of its oldest sea ice over the past three decades. Reports of the IPCC, based on thousands of peer reviewed science papers and reports, offer a confident documentation of past and present processes in the atmosphere.

On the other hand, when it comes to estimates of future ice melt and sea level rise rates, the IPCC models are subject to a number of uncertainties. This includes the difficulty in quantifying amplifying feedbacks from land and water, ice melt rates, linear versus irregular temperature trajectories, sea level rise rates, methane release rates, the role of fires, and the observed onset of transient freeze events.

Mass extinctions would follow abrupt climate changes

Linear to curved temperature trends of the types portrayed by the IPCC to the year 2300 are rare in the paleo-climate record, where abrupt warming and cooling are common during glacial and interglacial periods. At +4 degrees Celsius above pre-industrial temperature, projected by the IPCC for the end of the 21st century, life on Earth could be depleted to levels such as existed in the wake of previous mass extinctions of species.

There would be no smooth transition toward +4 degrees Celsius. Rather, there will be irregular heating, including a series of extreme weather events, and transient temperature reversals induced by the flow of cold ice melt water from the melting glacial sheets into the oceans.

Hansen et al (2016) used paleoclimate data and modern observations to estimate the effects of ice melt water from Greenland and Antarctica, with cold low-density meltwater capping warm subsurface ocean water. Ice mass loss would raise sea level by several and later tens of meters in an exponential rather than a linear response. Sharp drops in temperature, reflecting freeze events in the Atlantic Ocean and the sub-Antarctic Ocean and their surrounds, would reach -2 degrees C for several decades.

These projections differ markedly from IPCC models which portray long term ice melting values raising sea levels to less than 1.0 meters by the end of the 21st century, an estimate difficult to reconcile with satellite gravity-based mass loss estimates by Rignot et al (2011) and others.

Uncharted waters ahead

The world’s climate is moving into uncharted territory, with significant implications for the planning of future adaptation efforts, including preparations for sea level rise and for deep freeze events in parts of Western Europe and eastern North America. As the Earth warms, the increase in temperature contrasts across the globe, and thereby an increase in storminess and extreme weather events, as occur at present, need to be considered when planning adaptation measures. This would include channeling water from flooded areas to desiccated regions depending on environmental effects both in the source and in the destination areas.

Since many in authority do not accept, or only pay lip service to, climate science, it is a good question whether governments will be investing in adaptation measures in time. There is an urgent need to slow down and eventually arrest carbon emissions, since the average atmospheric level of carbon dioxide has already reached a level of 458.49 ppm CO2 (411.8 ppm CO2 + 46.69 ppm CO2 equivalent of methane). This generates amplifying feedbacks from land and oceans which include lesser CO2 sequestration by the oceans, desiccation of vegetation, fires, and release of methane from permafrost.

However, to date, no plans appear at hand for the draw-down of CO2 from the atmosphere on the required scale – the one measure which, in addition to marked decrease in carbon emissions, could potentially arrest global warming. In this regard, the reluctance to undertake meaningful mitigation measures does not bode well. The powers that be are now presiding over the greatest calamity that has ever befallen humanity and much of nature.

Dr Andrew Glikson is an Earth and paleo-climate scientist, who graduated at the University of Western Australia in 1968. He conducted geological surveys of the oldest geological formations in Australia, South Africa, India, and Canada, studied large asteroid impacts, including their effects on the atmosphere and the oceans, the effects of abrupt climate changes on the mass extinction of species, and the effects of climate and the mastery of fire on human evolution. Reprinted from John Menadue’s blog Pearls and Irritations.
Posted by on Mar 29 2019. Filed under Feature, Stewardship of our planet. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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