Warm/cool epochs over past 2000 years were regional until 20th century warming

Percentages of earth’s surface experiencing abnormal warm (red shading) and cold (blue shading) temperatures. Shading intensity indicates the magnitude of warmth and cold. a, Annual data. b, 51-year averaged data.

Over the last 2000 years Europe has experienced centennial scale cool and warm epochs including the Little Ice Age (1300 and 1850 CE), the Mediaeval Warm Period (800–1200 CE), the Dark Ages Cold Period (400–800 CE) and the Roman Warm Period (250 BCE to 400 CE). A recent analysis has generated spatial temporal temperature reconstructions covering the entire globe for the past 2,000 years. The research found no evidence that preindustrial cold and warm periods recorded in Europe and elsewhere extended over the entire globe. By contrast, the warmest period of the past 2,000 years occurred during the twentieth century for more than 98 per cent of the globe.

No evidence for globally coherent warm and cold periods over the preindustrial Common Era, Raphael Neukom, Nathan Steiger, Juan José Gómez-Navarro, Jianghao Wang & Johannes P. Werner, Nature, volume 571, pages 550–554 (2019).

From Our Files

Correlation of temperature and CO2 for last 420,000 years from Vostok

EC Perspective: Accounting for 800,000 years of climate change

Approximately 800,000 years ago something changed in the Earth’s climate system that led to the climate then following a series of approximately 100,000 year cycles. Small, predictable changes in the Earth’s orbit about the Sun act as triggers for the glacial and interglacial periods, but other factors such as ice sheet volume, CO2 concentration, and biological feedback mechanisms are also involved.

Temperature, CO2 and CH4 from Dome C ice core

Rising CO2 lagged Southern Hemisphere warming at the beginning of the last deglaciation

A new analysis of Antarctic ice cores shows that at the beginning of the last deglaciation, the start of rising CO2 lagged rising temperature by about 800 years which is consistent with the Southern Hemisphere playing a dominant role in the rise in atmospheric CO2. The concomitant rise in methane appears to be governed by Northern Hemisphere processes.

US projected and actual CO2 emissions 2005 to 2017

Emissions from electric power generation decoupled from economic growth in US

Between 2005 and 2017 the U.S. economy as measured by real GDP expanded by about 20 %. Over this same period, emissions from power generation dropped which is evidence of a decoupling between economic growth and power generation.

Upward revision of methane emissions from shale gas production could erode natural gas’ cleaner energy advantage

Evidence that methane emissions from natural gas production have been considerably underestimated by the EPA was recently reinforced by the initiation of an investigation into how the EPA estimates methane emissions by the EPA’s Inspector General. If it is found that emissions of methane from natural gas production are considerably greater than current estimates, the advantage that natural gas has over coal will be eroded and the advantage of switching to natural gas as a cleaner form of energy diminished.