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

Desdemona Despair

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-19^th-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 19^th 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