Since the 1970s, growing carbon dioxide emissions and resource depletion due to human activities have been raising concerns for global warming and climate change1. The science behind this phenomenon and its human cause is ever more unequivocal for every IPCC publication2. But this is not the first time there has been a great shift in the climate on Earth. How is the climate changing today? How did it change in the past and how will it be evolving in the future?
Climate variability in the past
The Earth, as one among many objects in space, is subject to several external variabilities. The way it rotates around its axis and how it orbits around the Sun is not constant but cyclical. The amount of solar irradiance received on the Earth’s surface has cycles as well3. As a result of these cycles, and other factors such as volcanic eruptions, environments and global temperatures have greatly varied over time. For instance, in the past 5,000 years, the planet has warmed by as much as 4 to 7ºC4.
How is the climate changing now?
The release of fossil fuel and other greenhouse gas emissions into the atmosphere have made climate change a large-scale phenomenon in a much shorter timeframe. As a result, living species cannot adapt as effectively. Moreover, extreme weather events are getting worse and more frequent5, causing more heat waves. NASA lists several other consequences to global warming: the temperature rise is leading to changes in precipitation patterns, sea level rise, stronger and more intense hurricanes, and the thawing of polar ice sheets6.
Future perspectives for the changing climate
The IPCC developed several scenario pathways that could happen from now to 2100. They are called “Representative Concentration Pathways” and represent the amount of greenhouse gas concentration in the atmosphere7. Where we stand along these pathways depends on the mitigation and adaptation measures to climate change that are taken. If we want to stay under the 1.5ºC warming advocated by the IPCC8, there is a need of more policymaking and cooperation between countries. Despite the United States withdrawing from the Paris Agreement in November 20199, countries around the world continue to stay committed to tacking the challenges of climate change10.
1 Meadows DH, Meadows DL, Randers J, Behrens III WW. The Limits to Growth. 1972.
2 IPCC Science report: climate change unequivocal, human influence at least 95% certain. European Commission. 2013 Sept 27.
3 Buis A. Why Milankovitch (Orbital) Cycles Can’t Explain Earth’s Current Warming. NASA Global Climate Change Blog. 2020 Feb 27.
4 Riebeek H. Global Warming. NASA Earth Observatory. 2010 June 3.
5 Russel R. Climate change and extreme weather: Science is proving the link. DW. 2018 April 11.
6 The Effects of Climate Change. NASA Global Climate Change Facts.
7 Climate Change 2014: Synthesis Report. IPCC. 2014.
8 Special Report: Global Warming of 1.5C. IPCC. 2018
9 Pompeo MR. On the U.S. withdrawal from the Paris Agreement. U.S. Department of State. 2019 Nov 4.
10 European Climate Change Programme. European Commission.
11 Image from NewClimate Institute