“Climate change is one of the defining issues of our time. It is now more certain than ever, based on many lines of evidence, that humans are changing Earth’s climate. The atmosphere and oceans have warmed, accompanied by sea-level rise, a strong decline in Arctic sea ice, and other climate-related changes.”

Dr. Ralph J. Cicerone (President, National Academy of Sciences) and Sir Paul Nurse (President, Royal Society)

 

On Thursday last week, the Royal Society and the US National Academy of Sciences, two of the most prestigious science academies in the world released an overview of “Climate Change: Evidence and Causes”. This publication aims to provide authoritative answers about climate science, and will serve as a key reference for a variety of people, including decision makers, policy makers, educators.  The report is freely available online, and will be distributed globally through non-governmental organisations.  The report outlines our current best understanding of climate change.  It is ground-breaking in that it is published through, and with the authority of, both the Royal Society and the National Academy of Sciences.   Its content underwent a rigorous peer-review process from a panel of 20 US and UK scientists, and provides answers to common questions about climate change in plain English.

The cover of the National Academy of Sciences and Royal Society Report

The cover of the National Academy of Sciences and Royal Society Report

Alongside the release, four of the report’s authors (Professor Eric Wolff, Professor Inez Fung, Sir Brian Hoskins, and Dr Ben Santer) hosted a live discussion seminar on the content of the document and answered questions.  We’ve highlighted a few of the key discussion points below:

  • As CO2 rises, further warming is predicted – if emissions continue at their current rate, warming of 2.6 – 4.8°C is predicted by 2100.  As well as this, even if we stopped all emissions today, it would take thousands of years for CO2 abundance to reduce, and for Earth’s temperature to reach pre-Industrial levels.
  • The increased CO2 in the atmosphere also dissolves in the oceans, forming a weak acid.  This has caused ocean acidification.
  • Though a change of only 2.6 – 4.8°C seems small, the last ice age was, on average, only 4-5°C colder than the present day.  These small temperature changes can be very disruptive, affecting regional and local temperatures more dramatically,causing changes in precipitation patterns, leading to large impacts upon ecosystems, and human society.
  • Through climate change, the Earth’s lower atmosphere is becoming warmer and moister.  This will provide more potential energy for weather events, meaning that heavy rainfall, snowfall, and drought events are becoming, and are likely to continue to become more frequent.  We do not yet fully understand the impact of climate change upon hurricanes and tornados.
  • Tipping points such as the shut-down of the North Atlantic Gulf Stream and catastrophic methane release are unlikely to be reached soon, however the possibility of abrupt change cannot be ruled out.
  • Science is based on a continual process of observation, understanding, modelling, testing, and prediction.  The main active research areas for climate science are now: cloud dynamics; centennial/decadal scale change; climate variations on regional-local scale.
  • Both models and observations are necessary for the progression of climate science. Models are checked by validation against palaeo-data.  What is more, model based estimates of temperature change are based upon what we have learned through palaeo-data, meaning that models may be conservative.
  • Technological advances are always improving the accuracy and precision of our models.  The two biggest ‘blind spots’ remaining in climate models are: the low resolution of weather systems (currently 100 km, 20 km is desired); and that we are unsure how atmospheric circulation varies due to the complex interactions of the atmospheric components.
  • Despite much publicity, the recent climate “pause” does not detract from the overall trend of climate warming.  Over long periods (centuries or millennia), climate change follows a trend similar to a staircase, a monotonic (steady, linear trend) warming trend was never predicted by climate scientists.  Sometimes temperature rises lots, sometimes not so much.  We must realise that when monitoring things, our frame of reference isn’t always long enough to make accurate interpretations of the longer-term trends.
  • Though reality shows less warming than predicted, there is no evidence to suggest that our models are invalidated. We have a good understanding of the forces that have led to the temporary climate “slow down”. There are lots of factors which have contributed to this within the earth system, such as large volcanic eruptions.

Have a look at the full document on the Royal Society’s website and look for any news on Twitter through #NASRSclimate.  Video of this event will be available on their website in week commencing Monday 3 March 2014.