Understanding Global Warming
Global warming refers to the long-term rise in Earth's average surface temperature. More specifically, it usually describes the increase in global temperatures since the Industrial Revolution. Since 1850, Earth's surface temperature has risen by over 1°C. The Intergovernmental Panel on Climate Change (IPCC) concluded in its 2013 report that there is a 95% certainty this warming is due to human activities, primarily the increase in greenhouse gases like carbon dioxide.
The Current Trend in Global Warming
Starting from 1850, the year often marked as the beginning of extensive temperature measurements and the Industrial Revolution, global temperatures have steadily climbed. By the end of 2017, the Earth’s surface temperature had risen by more than 1°C compared to pre-industrial levels. Notably, the pace of warming accelerated in the 20th century, especially after 1900. While certain periods experienced pauses in this trend, such as between 1950-1975 and 1998-2013, the warming pattern resumed after 2014, with 2016 being the hottest year on record, followed closely by 2017.
If greenhouse gas emissions continue at their current rate, the IPCC estimates that by 2100, the global surface temperature could rise by 4°C to 5°C compared to pre-industrial levels. Such warming would have widespread, irreversible effects on ecosystems and human societies, prompting international efforts like the Paris Agreement of 2015, which aims to limit temperature rises to below 1.5°C.
Causes of Global Warming
In 1850, atmospheric carbon dioxide (CO2) levels were around 280 parts per million (ppm). By December 2017, this figure had soared to about 405 ppm, and without intervention, CO2 levels are expected to exceed 450 ppm by 2050. The primary driver of this increase is human activity, especially the burning of fossil fuels. The IPCC's 5th report highlights that natural factors like volcanic eruptions and solar variations have had minimal influence on the warming observed since the Industrial Revolution.
Among the key contributors to the greenhouse effect, CO2 accounts for roughly 60%, while methane and ozone contribute 15% and 8%, respectively.
Impacts of Global Warming
The consequences of human-induced global warming extend far beyond temperature increases. The world is also experiencing rising sea levels, ocean acidification, disruptions in water cycles, and biodiversity loss. By 2013, sea levels had risen 19 cm compared to pre-industrial times. Although global temperatures stabilized from 1998-2013, sea levels continued to rise, with the rate accelerating after 1995.
If global temperatures rise by more than 2°C, sea levels could increase by 1 to 4 meters due to thermal expansion of water and the melting of ice sheets. Meanwhile, ocean acidification is another growing concern. Oceans have absorbed a significant portion of the excess CO2 from fossil fuel combustion, resulting in a 25-30% increase in ocean acidity since the Industrial Revolution. This process threatens marine life, particularly coral reefs, many of which are now at risk of extinction due to bleaching and other stress factors.
Effects on Ecosystems
On land, ecosystems are being impacted by earlier springs, with species migrating northward or to higher altitudes. Many species are also facing extinction, leading to reduced biodiversity. The ripple effect of these changes will continue to affect ecosystems and human societies alike, making climate change one of the most critical challenges of our time.
References
1. IPCC Reports
2. Kosaka, Y. & Xie, S.-P. (2013). 'Recent global-warming hiatus tied to equatorial Pacific surface cooling'. Nature.
3. Meehl, G.A. et al. (2013). 'Externally forced and internally generated decadal climate variability'. Journal of Climate.
4. Paris Agreement (2015). United Nations Treaty Collection.
5. CO2.Earth (2016).
6. Zeebe, R.E. (2012). 'History of Seawater Carbonate Chemistry and Ocean Acidification'. Annual Review of Earth and Planetary Sciences.
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