2°C, just a matter of warmer days?

In December 2015, Parties to the UNFCCC gathered at COP21 in Paris to discuss common international action to fight climate change and to adapt to its consequences. COP21 resulted in the Paris Agreement or more simply known as “the 2°C”. The reason being is that this agreement aims to maintain the global temperature rise below 2°C by 2100 compared to pre-industrial levels (UNFCCC). As of April 2016, 190 Parties covering almost 95% of the world CO2 emissions had submitted an Intended Nationally Determined Contribution (INDC). The INDCs represent the efforts that each country is committed to make at a national scale to mitigate climate change (UNFCCC)

Given the media coverage of the COP21 and international climate discussions, the 2°C target seems like an important issue that should be diffused to the general public. Yet, why is such a crucial issue embodied by a target as meaningless as 2°C by 2100? The daily temperature might fluctuate by way more than 2°C, and yet, most people survive. Focusing on 2100 as the main time horizon also suggests that we have much time to sort out the problem. Moreover, between 1880 and 2012, the global temperature of the Earth has already risen by 0.85°C (IPCC, 2013) without undermining the development of our civilisation. So why should we be afraid of 2°C by 2100 besides the fact that humanity has already withstood almost 1°C of global temperature rise in the last century?

The answer lies in the fact that our senses are not made to fathom an average global temperature change of 2°C. The temperature that you can feel right now while reading this article is the instant temperature at the very location you are in which is a consequence of the weather. However, weather is not climate. Climate science studies the behaviour of the atmosphere over long periods (decades, centuries, millennials) whereas weather gives a description of the state of the atmosphere over much shorter periods (hours, days, weeks) (NASA, 2005).

If senses are not adapted to understand climate, what reference can we have?

Palaeoclimatology which is the study of the history of the Earth’s climate is an insightful proxy to depict what several degrees represent at the scale of the Earth. When the last glacial period peaked 21,000 years ago (also known as the Last Glacial Maximum), the mean temperature of the Earth was “only” around 4°C lower than what it is now (Annan & Hargreaves, 2013; Jansen et al., 2007) but these few degrees had severe implications. At that time, sea level was 120m lower than at present (Jansen et al., 2007) and ecosystems were very different. For example, the figure below shows the difference of vegetation in Australia between the Last Glacial Maximum and the present (Adams & Faure, 1997). It is estimated that Australia was mainly covered by dunefields, Tasmania was connected to the mainland, the rainfall of central Australia was about half of the present levels, and 85% of the continent was treeless (Monroe, 2015).

This massive change in the Earth’s climate was triggered by orbital forces as described by the Milankovitch theory. Periodic fluctuations in the Earth’s obliquity, eccentricity and precession change the average solar insolation received by our planet which in turn causes climate oscillations on a geological timescale (Jansen et al., 2007). Therefore, it is correct to say that the Earth’s climate has always naturally fluctuated over time. However, the rate of global warming we are currently experiencing is unprecedented. The transition from the Last Glacial Maximum to the present climate occurred at an average rate about 10 times lower than the warming of the 20th century (Jansen et al., 2007). One of the consequences of that rapid rate of change is that ecosystems do not have as much time to adapt as if the warming occurred naturally over thousands of years.

What symptoms can be expected from the ongoing climate change?

Earth is comparable to the human body in the sense that it is a complex system that has a steady operating regime at a given geological time. Imagine that you get sick and your body temperature which is normally around 37°C raises to 39°C within a couple of hours because of the fever. Although it represents “only” 2°C of warming, you can feel that you are not in a normal equilibrium state anymore and your body fights to recover. When you reach such a state of illness, what are you really suffering from: the heat or the pain caused by side effects? The real concern about climate change is actually not the rise in the average global temperature but all the threatening impacts that it brings about. Greenhouse gases are comparable to an external source of pressure to which the climate responds. The Earth’s immune system takes many forms

• Change in rainfall patterns affecting water resources and agriculture productivity. The average annual water flow into Perth dams has decreased almost sixfold from the period 1911-1974 to the period 2006-2010 (Climate Commission, 2013).
• Increase in extreme events (frequency, intensity, length) such as droughts, heatwaves and flooding. By 2050, heatwaves are projected to cause hundreds of additional deaths annually in Australia (Hughes, Hanna, & Fenwick, 2016).
• Increase in bushfires. The total economic costs of NSW and ACT bushfires are estimated to be approximately $100m and they could potentially reach $232m by 2050. (Hughes & Alexander, 2016)

• Rise of the sea level driven by ice melting and thermal expansion of water. In Australia, $226bn worth of infrastructure and homes are at risk from coastal flooding at projected sea level rise (Steffen, Hunter, & Hughes, 2014).

• Increase in ocean acidity and marine heatwaves, two major sources of stress for the Great Barrier Reef.

Hence, 2°C of warming at the scale of the Earth is much more than a matter of warmer days. Some of the impacts of climate change are foreseen to be massive, abrupt and disruptive to several billions of sedentary humans.

Now let’s assume that, according to your GP, the likely origin of your disease is the tobacco addiction that you have had for 20 years. Therefore, he urgently recommends you to quit smoking, but just as every addiction, it takes a long and painful process. Energy from fossil fuels is an addiction that has been sustaining human development since the industrial revolution. Now that the impacts of climate change are already looming upon us, we seek to conquer that addiction which will likely take a long and painful process indeed. As put forward by the Climate Council of Australia: “Climate change is one of the largest long-term, global challenges humans have ever faced in the history of civilisation”.

Elliot MARI
Energy Researcher at Sustainable Energy Network Solutions