> One common metric used to investigate the effects of global warming is known as “equilibrium climate sensitivity”, defined as the full amount of global surfac

> One common metric used to investigate the effects of global warming is known as “equilibrium climate sensitivity”, defined as the full amount of global surface warming that will eventually occur in response to a doubling of atmospheric CO2 concentrations compared to pre-industrial times. The article bases its warning on this "equilibrium climate sensitivity" metric (aka "sensitivity"). This widely-used benchmarks allows the many different lines of evidence to be used together and translated into real-world effects. The article cites a pre-industrial CO2 measurement of 280ppm, and a current measurement of 410ppm. If current trends hold, the doubling point (560ppm CO2) will occur in 2060. The rest of the article deals with models that are predicting much higher sensitivity than earlier models. In 2013 the estimate was 1.5 - 4.5 degrees C. The new models are predicting 2.8 - 5.8 degrees C, with eight of the (unknown total) models predicting 5 degrees or higher. These results are scheduled to be published in the 2021 IPCC report. For comparison, the Paris Agreement seeks to limit temperature increases to no more than 2 degrees C. What would 5 degrees C warming mean for the Earth? > The most comprehensive summary of conditions experienced during past warm periods in the Earth’s recent history was published in June 2018 ... by 59 leading experts from 17 countries. The report concluded that warming of between 1.5 and 2°C in the past was enough to see significant shifts in climate zones, and land and aquatic ecosystems “spatially reorganize”. > These changes triggered substantial long-term melting of ice in Greenland and Antarctica, unleashing 6 to 13 metres of global sea-level rise lasting thousands of years. To the extent that the models are right and the study of past warming incidents applies in the future, we can expect sea level rises in excess of 6 - 13 meters (lasting thousands of years) by 2060 and significant shifts in climate zones.