Global Warming Index from Jan 1950 to May 2017 for HadCRUT4. The anthropogenic contribution in orange (with 5–95% confidence interval). The natural contribution (solar and volcanic) in blue. The red line shows the combined (total) externally-driven temperature change. The dark red line shows the evolution of the GWI when only past forcing and temperature data are used. It starts in 1944 - the time when a human-induced warming signal can first be detected - followed by a new data point for each month up until May 2017. The evolution of the red line indicates the degree of month-to-month variability of the index. The thin black line are the monthly (HadCRUT4) GMST data. For illustration, blue diamonds indicate when major climate summits took place in context of the monthly GMST at that time. Graphic: Haustein, et al., 2017 / Scientific Reports

13 November 2017 (University of Oxford) – A new index of warming due to human influence on climate is released today in the journal Nature Scientific Reports. It exceeded 1°C above mid-19th-century levels in 2017 and is rising faster than ever before, leaving little time to achieve the goals of the Paris Climate Agreement.

"Global temperatures may be pushed up temporarily by El Niño events or down by volcanic eruptions. We combine temperature observations with measurements of drivers of climate change to provide an up-to-date estimate of the contribution of human influence to global warming", explains Karsten Haustein, who led the study.

The level of human-induced warming reached 1.02°C above the average for 1850-79 in November 2017 (with a 5-95% uncertainty range of 0.88-1.22°C) based on HadCRUT4 temperature dataset from the UK Met Office, or 1.08°C when estimated using a version of HadCRUT4 (Cowtan/Way) that interpolates over poorly-sampled regions like the Arctic.

This figure is updated continuously on www.globalwarmingindex.org

"This 'Global Warming Index' has been increasing continuously since the 19th century, with no pause in recent decades", Haustein continues. "It has risen at a rate of 0.16°C per decade over the past 20 years, and is expected to average 0.96°C above 1850-79 for the decade 2010-2019. Worryingly, it appears to be accelerating, despite the recent slow-down in carbon dioxide emissions, because of trends in other climate pollutants, notably methane."

"A robust, continuously-updated index of human-induced warming - the only component of global temperatures we have any control over - is essential to monitor progress towards meeting temperature goals" notes David Frame, a study co-author. "We hope the 'Global Warming Index' will provide this essential information to the UNFCCC process."

Using our index in conjunction with carbon budget estimates based on current emissions, the remaining time until we cross the (anthropogenic) warming target of 1.5°C or 2°C can be monitored continuously as well on www.climateclock.net

The paper is freely available online at www.nature.com/articles/s41598-017-14828-5.

These results will be presented to delegates of the UNFCCC COP23 at a side-event "Measuring progress towards Paris Agreement goals: aligning science and policy". Venue: Bonn Zone Meeting Room 11, 15:00-16:30, Monday 13 November.

New index of human influence on global temperature is rising faster than ever


ABSTRACT: We propose a simple real-time index of global human-induced warming and assess its robustness to uncertainties in climate forcing and short-term climate fluctuations. This index provides improved scientific context for temperature stabilisation targets and has the potential to decrease the volatility of climate policy. We quantify uncertainties arising from temperature observations, climate radiative forcings, internal variability and the model response. Our index and the associated rate of human-induced warming is compatible with a range of other more sophisticated methods to estimate the human contribution to observed global temperature change.

A real-time Global Warming Index

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