Dr Jan Zika, NERC Independent Research Fellow in the Department of Physics and a Grantham Affiliate explains why we need brilliant climate scientists now more than ever before.
In 1560, our moon did something that it does only every generation or so. As it circled the Earth at a stately pace of one rotation per 27 days, it found itself directly between us and the Sun. This cast a great shadow over Europe, causing great panic.
Remarkably for this period, 400 years before humans left the Earth and set foot on the dusty lunar surface, this mystical and awe-inspiring occurrence was predicted by the Copernican model of the cosmos. Moved by the power of this new science, an unassuming young Danish scholar called Tycho Brahe decided to dedicate his superior intellect to studying the stars.
He fast became one of great thinkers of the Renaissance and was one of the first to question the belief that the universe is unchanging. Now in 2015, our home planet is at risk from the less visible, but far less benign shadow of climate change. Are we due a new generation of Brahes, great thinkers who can propel our understanding forward?
There is no better test of a science than its ability to make and verify predictions. In the late 19th century, Arheneous first proposed a theory that a blanket of certain gases in the atmosphere was helping to insulate the planet. Over a century later, there is still an astronomical amount we don’t fully understand about our planet’s climate system.
A delicate heat balance
The climate turns out not to be as predictable as Brahe’s eclipse. We humans exist within a thin fraction of the climate system; typically experiencing winds from the lowest kilometre of the atmosphere and ocean currents from the shallowest 50 metres of the ocean.
We can think of the temperature in this zone like a variable bank balance. Solar radiation deposits a continuous stream of income, heat radiated out to space is like our regular spending, and savings are made for a later date as heat deposited into the deep ocean.
Basic physics tells us that greenhouse gases reduce the amount of heat lost to space. In the absence of other effects, the balance of heat grows in the thin layer we occupy. Just as unexpected bills affect our own bank balance though, a plethora of changeable processes affect Earth’s surface temperature.
The ocean as a heat sink
One of these processes, which sees heat being stored in the ocean, can lead to a slowing and even temporary reversal of surface warming. Between 1997 and 2014, the earth did warm, but at a slower pace than it had before – in large part due to increased storage of heat in the ocean – the reasons for which we discuss in a recent Grantham briefing paper.
From studying this period of slower warming we have learnt a great deal about the climate system, including that the winds along the equator that expose deep cold water to the surface are more variable from decade to decade in the real climate than in the computer models that have so far been used to predict future temperatures.
Cycles in the oceans’ circulation are now giving back some of this heat, and aided by a record El Niño, 2015 is most likely to be earth’s warmest year on record. Continuing the trend from 2014, the current title-holder according to the World Meteorological Organisation. The prediction, made by scientists in the 1970s and 80s, and heard by the public at large in the 1990s, is emerging once again.
What’s the forecast?
Ocean circulation may still cause the decade following this one to be cooler than the present. It could also be far, far warmer, we don’t yet know. The same goes for the plethora of processes, which affect the surface temperature and climate at large scales. The list of largely unpredictable phenomena includes the physics of clouds, the effect of erupting volcanoes, variability in radiation from the sun and the cooling effects of atmospheric pollutants.
To help understand and predict these effects better we need the support of public and private donors and we need great minds to take to climate science in 2015, like Tycho Brahe took to astronomy in the 1560.
Regardless of whether the COP21 meeting in Paris yields significant pledges to cut greenhouse gas emissions, understanding of climate science will become more and more important.
As the Grantham Institute’s climate prediction tool shows, pledges from governments, put the world on course for well over 2oC of global warming.
Brahe may have become an astronomer on the basis of a visible yet benign prediction. The predictions made about the effects of the changing climate have been less visible but are becoming less and less benign. Let us hope the Tycho Brahes of today have been taking note.
