The outcome of the ANCs long-awaited KwaZulu-Natal conference was a win for the Thuma Mina crowd. (Delwyn Verasamy/M&G)
Climatic changes have happened before due to natural forces — they have sometimes been extreme, and resulted in major extinctions. Over the last 800 000 years, scientists are pretty certain that the Earth has warmed and cooled very significantly at least 20 times, with glaciers retreating and advancing and sea levels rising and falling in response.
Sometimes changes have been rapid and extreme, with mean temperatures fluctuating by more than 2°C in just 50 to 100 years. The difference this time around is that people are contributing to the Earth’s climate changes.
In 2014 the Nobel Peace Prize-winning Intergovernmental Panel on Climate Change concluded that at least half of the warming observed globally over the past six decades is due to human activity (primarily the burning of fossil fuels — coal, gas and oil — and deforestation). Global temperatures are rising higher and faster than can be explained by phenomena such as solar activity. Instead, rising temperatures mirror increases in the concentrations of “greenhouse gases”.
Gases like carbon dioxide (CO2) and methane naturally trap heat in the atmosphere, helping to maintain a habitable planet. But in the last 150 years, since fossil fuels began powering the industrialised world, CO2 levels have increased by more than 40%, causing extra heat to be trapped in the atmosphere and making the Earth’s surface warmer. We are starting to feel the effects of an atmosphere and biosphere significantly changed by the by-products of progress.
The results of the study have been published in a new publication, Change is in the Air, which was launched at the Department of Science and Technology’s First Science Forum (www.sfsa.co.za) held in Pretoria between 8 and 9 December.
The publication can be downloaded from the SAEON website: (www.saeon.ac.za)
Fact!
The concentration of CO2 in the atmosphere has increased by more than 40% since the dawn of the industrial revolution, and is now higher than it has been in the past 800 000 years.
The rate of increase in CO2 has been accelerating in the past two decades, to the extent that actual CO2 increases have exceeded predictions.
Is the climate really changing? Draw your own conclusions:
• Global sea levels rose 10 to 25 cm in the last century.
• Each of the previous three decades has been successively warmer than any preceding decade since records began.
• In the Northern hemisphere the 30-year period from 1983 to 2012 was likely the warmest 30-year period in the last 1 400 years.
• The late summer and early autumn Arctic sea-ice thickness has declined by 40% in the last 30 years.
• The extent of Northern hemisphere snow cover has decreased by 10% since global observations became available in the late 1960s.
• Many species have shifted their geographic ranges, seasonal activities and migration patterns in response to ongoing climate change.
• In a study of 329 plant and animal species, 84% had shifted their ranges towards the cooler poles, or to higher elevations.