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

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.

Comparison of temperature and CO2 from Vostok ice cores

Close correlation of temperature and greenhouse gas concentrations over the last four glacial-interglacial cycles

In January 1998, a collaborative ice-drilling project between Russia, the United States, and France at the Russian Vostok revealed that over the past four cycles atmospheric concentration of carbon dioxide correlates closely with Antarctic air-temperature. The analysis also suggests a sequence of events that is characteristic of every termination; warming by orbital forcing, then increasing greenhouse gases, and followed by ice sheet melting and reduced albedo.

Low cost sensor enables citizen scientists to measure and share urban air pollution data over the web

Based on the latest results from WHO air pollution is now the world’s largest single environmental health risk, linked to 12% of all global deaths. Citizen scientists can contribute to measuring air pollution using a low cost sensor measuring atmospheric particulate matter and share the measurements via open source geospatial web mapping software.

Temperature and atmospheric CO2 from Dome C for 800 000 years

Observed coupling between surface temperature and atmospheric CO2 extended to 1.5 million years ago

Evidence from Antarctic ice cores have revealed a close correlation between surface temperature and atmospheric carbon dioxide concentration for the past 800,000 years (excluding the immediate present.) A recent analysis of Antarctic blue ice has found that the close correlation between temperature CO2 extends to 1.5 million years ago during the time when the glacial/interglacial period was 40,000 years.