Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change
This deceptively simple idea binds the world together in fighting perhaps our greatest, most complicated existential threat today.
But why is 2 degrees that big a deal when we have daily swings in temperature of tens of degrees? Paris, for instance, today will experience a minimum of 10 degrees and a maximum of 21 degrees.
“Would a 2 degree rise kill us? Wouldn’t it just lead to marginally warmer days throughout the year? And while we might not like the extra warmth, wouldn’t life go on more or less the same way it always has?” This was my thought process, until the 1 degree temperature rise that we have already experienced since the beginning of the 19th century brought with it mounting climate catastrophes across the globe. Heat waves, droughts, record breaking temperatures, forest fires, hurricanes, floods all made it clear that life would definitely not go on the same way if temperatures rose another degree. What remained less clear was how just a 1 degree change was causing so much damage- until I focused on two words in that deceptively simple idea-’global average’.
The global average temperature is derived from daily temperature readings taken at thousands of weather stations (approximately 6300) across the globe. Due to the simplistic nature of the number, it hides two extremely important data points:
A temperature map derived from data collected by GISS NASA, which is one of the established authorities on climate science, serves to illustrate point 1 and is given below. The map shows the difference in average annual temperature across various regions of the globe in 2016 compared to the average annual temperature in those regions from 1900–1930.
The number at the top right corner of the map-1.28 degrees is the increase in global average annual temperature in 2016 compared to 1900–1930 average. But as can be seen from the map, the 1.28 degrees number hides the fact that parts of Europe, Middle East, South America, Africa and North America have warmed by over 2 degrees already and parts of Arctic have warmed an alarming 4 degrees already.
Since oceans cover 71% of the Earth’s surface, the lesser extent of warming over the water brings down the global average and hides behind it the devastating changes underway in the global weather system. The Arctic warming especially has seriously worrying implications for sea level rise and changes in ocean currents. Seen in this light the 2 degree number committed at Paris suddenly seems much larger.
The second point raised above, about how temperatures vary at any one place through the year, is best illustrated with an example. Given below is a hypothetical temperature trend for New Delhi over 10 days in 1900 (in blue) and 2016 (in red):
As can be seen above, temperatures in 2016 are higher than 1900, on some days by as much as 4–5 degrees and hitting 50 degrees- a temperature which would lead to severe heat stress and many fatalities. But if we look at the daily temperature difference over this 10 day period given in the graph below, we realize that the average temperature has only risen by 2 degrees.
This is the second fact which the 2 degree average number hides- that a lot of the temperature increase will be experienced over few extremely hot days in summers in the form of heat waves, with temperatures shooting up 5–10 degrees over normal, making stepping out possibly fatal- as it was for thousands of people in India alone in the last few years. An increase of 2 degrees in global average temperatures can most certainly kill us.
While the temperature trend in the example above is a hypothetical one, this heat stress in summers has already become a reality with just 1 degree rise- 30% of the world’s population today is exposed to deadly heat at least 20 days in a year. This number is expected to rise to over 70% if we continue on our fossil fuel driven trajectory.
And while we are discussing the impact of just 2 degrees, business as usual scenario puts us on course for a 4 degree temperature rise by the of the century. To get an idea of what that can do, we only need to look at the last ice age 14000 years ago. Temperatures during this period were lower by just 5 degrees than they are today, but this was enough to ensure North America was covered under a 3 kilometer ice sheet.
Modern civilization, as we know it, began with the discovery of agriculture 10,000 years ago. Conditions over these last 10,000 years have been especially conducive for us to flourish, temperatures having been constricted to a 1 degree band over modern day averages. But in this epoch, the anthropocene- the age of man, we are now already outside that band and along with the rest of the planet are about to pay the price for our own unbridled progress.
We would do well to revisit our history, pay heed to the destruction already taking place around us and change course swiftly. Because sure, 2 degrees doesn’t sound like much, but as someone once told me-it is the difference between ice and water.