Hothouse earth – long hot summer and extreme weather events strengthens consensus on climate change

Hothouse earth image

The UK has recently been experiencing the type of prolonged hot spell that hasn’t been seen since the summer of 1976.  In that year the government of the day introduced a Drought Act and even appointed a Minister for Drought, Denis Howell, whose job was to encourage the public to use less water.

While a very wet (and cold) Spring and Winters saved us from serious water shortages, 1976 was a freakishly hot year but was a local effect, confined to the UK with generally average temperatures seen in other countries.

2018 vs 1976 UK comparison

In the intervening 42 years the average global temperature has crept up and is set to rise further.

Hottest years

Globally, the hottest years have been since 1995. Combining the data sets from NOAA (National Oceanic and Atmospheric Administration) and NASA (National Aeronautics and Space Administration) finds the following:

  • The five warmest years in the global record have all come in the 2010s
  • The 10 warmest years on record have all come since 1998
  • The 20 warmest years on record have all come since 1995

Hottest years globally

The trend is clear that recent years have been the hottest on record with 2017 being the third hottest on record.

Extreme weather events in 2018

There is now a general acceptance among the general public that our climate has changed and we are seeing the effects of climate change and extreme temperatures across the globe:

These are all consequences of extreme weather and scientists are starting to get less cautious about correlating specific events with the effects of climate change.

Hothouse earth – when the Earth passes a tipping point

The term ‘hothouse earth’ is starting to emerge which refers an unassailable tipping point beyond which the Earth’s natural cooling systems start to unravel.

Hothouse earth events
Global map of potential tipping cascades. The individual tipping elements are color- coded according to estimated thresholds in global average surface temperature (tipping points) (12, 34). Arrows show the potential interactions among the tipping elements based on expert elicitation that could generate cascades. Note that, although the risk for tipping (loss of) the East Antarctic Ice Sheet is proposed at >5 °C, some marine-based sectors in East Antarctica may be vulnerable at lower temperatures. Copyright 2018 National Academy of Sciences. Source: Trajectories of the Earth System in the Anthropocene – http://www.pnas.org/content/early/2018/08/07/1810141115

In the journal Proceedings of the National Academy of Sciences of the United States of America the rather soberly entitled paper ‘Trajectories of the Earth System in the Anthropocene’ the authors “explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced.”

Their analysis is not conclusive, but warn the Paris commitment to keep warming at 2C above pre-industrial levels may not be enough to “park” the planet’s climate at a stable temperature.

They warn that the hothouse trajectory “would almost certainly flood deltaic environments, increase the risk of damage from coastal storms, and eliminate coral reefs (and all of the benefits that they provide for societies) by the end of this century or earlier.”

“I do hope we are wrong, but as scientists we have a responsibility to explore whether this is real,” said Johan Rockström, executive director of the Stockholm Resilience Centre. “We need to know now. It’s so urgent. This is one of the most existential questions in science.”Hothouse earth image

Rockström and his co-authors are among the world’s leading authorities on positive feedback loops, by which warming temperatures release new sources of greenhouse gases or destroy the Earth’s ability to absorb carbon or reflect heat.

The combination and interrelation of these events could lead to the type of runaway, uncontrollable heating that has been warned of for many years. Let’s hope it is not too late to act.

Further reading

Domino effect of climate events could push earth into hothouse state

Trajectories of the Earth System in the Anthropocene

http://www.climatecentral.org/gallery/graphics/the-10-hottest-global-years-on-record

1976 summer in the UK compared to 2018

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