When Did Global Warming Start?

What were the first signals of climate change? When exactly did global warming first begin? Some climatologists say it started around 1720. Others say it began in 1780 due to increased coal consumption during the Industrial Revolution. Meantime, the IPCC uses an 1850-1900 baseline to calculate the ensuing rise in global temperature. This article explains all you need to know.
Late 19th Century: The Start Of Global Warming
Manchester, England. Late 19th century.

Lack of Precise Information About the History of Climate Change

When did the first signs of climate change appear? When did global warming start? In other words, when did Earth’s temperature start rising because of fossil fuels like coal? And if we can’t say for sure, then what date are we going to use as a starting point, so we can measure the rate of increase in global temperature, and fine tune our climate action plan accordingly?

Amazingly, we still don’t have clear answers to these questions because we lack precise information about the history of climate change and what was happening to our climate system before 1850 – the date when global records first began. 1 What’s more, neither the UN Framework Convention on Climate Change (UNFCCC) nor the Intergovernmental Panel on Climate Change (IPCC) have officially defined when warming began. The most common approach is to use 1850-1900 as an artificial “pre-industrial baseline”, since when scientists believe that the world has warmed by just over 1°C.

Earth's Average Temperature Chart showing the effects of global warming
Global mean surface temperatures since 1880. Source: NASA

Global Warming: The Beginning

The later part of the 19th century is commonly regarded as the point at which increased energy consumption of coal and oil started to influence the climate. However, coal was being mined and used in large quantities from 1750 onwards, so it’s likely that the effects of fossil fuels were becoming apparent well before the late 19th century.

It was the Industrial Revolution that started it. It created a massive demand for coal (a) to power steam engines and other machines, (b) to power new factories and industrial processes, and (c) to power the new steamships. It was the demand for coal for ships that stimulated mining around the globe.

In 1700, Britain was producing 2.6 million tons of coal a year. By 1750, annual production was 5.2 million tons; by 1795, it was 10 million tons. 2 In 1800, Britain accounted for 90 percent of world output. 3 By 1850, annual production was 62.5 million tons per year – more than ten times greater than in 1750. 4

Although coal production skyrocketed in America during the early 19th century, doubling or tripling every decade, followed mid-century by rapidly increasing oil/petroleum production, it was British coal that kick-started climate change through its greenhouse gas emissions of (mostly) carbon dioxide (CO2) and methane (CH4).

By 1905, however, it was a different story. The United States had overtaken Britain to become the world’s leading coal producer, while Germany was catching up fast.

Worldwide Coal Production Levels at the start of global warming
Source: “Coal.” (1911) Hilary Bauerman. [Bauerman, Hilary (1911). “Coal” . In Chisholm, Hugh (ed.). Encyclopedia Britannica. 6 (11th ed.). Cambridge University Press. p. 579.] [“World Energy Production 1800-1985.” Bouda Etemad and Jean Luciani. ISBN 2-600-56007-6.]

When exactly was the Industrial Revolution?

There is no exact date for either the beginning or the end of the Industrial Revolution. However, the name was first popularized by the English historian and scholar Arnold Toynbee (1852–83), to describe Britain’s economic development during the 80-year period from 1760 to 1840.

The original Industrial Revolution is quite separate from the so-called ‘second Industrial Revolution’, which peaked between 1870 and 1914, the ‘third industrial revolution’ which began in the 1950s, and a fourth version, which is still emerging.

Marine Fossils Show Global Warming Started In 1830s

In view of this early use of coal and the resulting greenhouse gases, it’s no surprise that a recent study, published in Nature, shows climate change beginning in the 1830s. 5

The study’s findings are based on an assessment of tropical sea surface temperatures captured in fossilised corals and tiny marine organisms. Known as “climate proxies”, the remains of these creatures, long buried in seabed sediments, carry the marks of past ocean temperatures. Along with ice cores and tree rings, they offer a glimpse of land temperatures throughout Earth’s history.

Oceans are actually critical to our understanding of Earth’s climate, because 93 percent of the heat that reaches Earth’s surface is absorbed by the sea. Up to now, measurements obtained from instrumental temperature records show rising temperatures first appearing in the tropical ocean during the 1950s. The above Nature study augments the official record with data captured in the proxy record, and traces the start of global warming back to the 1830s.

According to Professor Nerilie Abram, the study’s lead author, “Somebody living in the 1830s or even the 1890s would not have been able to distinguish that there was this change afoot,” she says. “It’s by having this long record now that extends almost 200 years from that point that we can go back and say ‘Well, this was when the changes first started.’”

Climate Change for Beginners
Climate Change for Students

What Is The Official Starting Point For Global Warming?

Although the UN Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC) use terms like “pre-industrial levels”, to describe greenhouse gas levels before the Industrial Revolution, they don’t define or explain exactly when this pre-industrial era ended and the “industrial” one began. Instead they refer to GHG levels “before 1850” or “from 1880 onwards” or “before the Industrial Revolution”.

In recent years, “pre-industrial” has become associated with the period 1850-1900, because 1850 saw the introduction of global temperature measurements. It is sometimes referred to as the “pre-industrial baseline 1850-1900.” The first organization to tie “pre-industrial” to the period 1850-1900 was the World Bank in its 2014 report “Turn Down the Heat”, which was prepared by the Potsdam Institute for Climate Impact Research and the climate think-tank Climate Analytics.

In the same year, the IPCC (in its Fifth Assessment Report) began using the period 1850-1900 as a specific reference point for the start of global warming, but without explaining its full significance as being representative of pre-industrial times.

A year later, the UNFCCC accepted the late 19th century (specifically the year 1880) as the best period to represent the “pre-industrial” situation, rather than the year 1750. 6

Since then, the IPCC has produced a slew of reports, including its Special Report on Global Warming of 1.5 °C, but has omitted to clarify the starting point from when the global temperature increase of “1.5 °C” is measured.

So When Did Global Warming Start? Scientists Can’t Agree 

According to the UK Met Office (Jan 2017), when compared with the 1850 to 1900 baseline, the 2016 average global temperature anomaly was around 1.1 °C (roughly 1.91 °F). 7

Around the same time, two studies provoked debate within the scientific community about whether this figure is correct. One study (Schurer) maintained the temperature rise is 1.2 °C (2.2 °F) 8 ; the other (Millar) argued that the rise is 0.9° C (1.6° F). 9

Schurer argues for using earlier time periods (1400-1800) as a baseline. This is because some man-made warming may have taken place earlier. This earlier baseline nets an additional two tenths of warming. The conclusion is that the world is closer to the targets of 1.5 °C and 2.0 °C, therefore greater cuts in carbon emissions are needed. Millar used the UK Hadley Centre global surface temperature dataset “HadCRUT4”, which uses 1850 as the starting point and estimates global surface temperatures have risen by 0.9°C since that time. Millar’s position is that the 1.5 °C target can be achieved with less strict reductions, using a carbon budget of more than 15 years of current emissions, fo a 66 percent chance of limiting temperature rise to 1.5 °C. This is larger than most other estimates.

Another study (Hawkins), proposes a pre-industrial baseline of 1720–1800 for the start of global warming. 10 It claims that this period is most suitable to be defined as preindustrial in physical terms, despite its reliance on climate proxies to set a starting temperature.

Arguments for earlier baselines (Schurer and Hawkins) are more difficult to sustain than those favoring the conventional 1850-1900 baseline. The most obvious drawback is their reliance on climate proxies, such as tree rings, ice cores, corals and pollens. These have well-documented inaccuracies and difficulties. 11

But Millar’s position isn’t totally solid either. The HadCRUT4 system, upon which it is based, has some significant flaws. 12 To begin with, it only covers 84 percent of Earth’s surface. There are gaps in its coverage, notably in the Arctic which happens to be the fastest-warming part of the planet. 13 As a result, HadCRUT4 somewhat underestimates global warming.

Natural Warming After The Little Ice Age

Probably the biggest problem facing earlier baselines is the Little Ice Age, which lasted very approximately between 1300 and 1850. During this period average temperatures were lower than normal. And when the period of was over, it would be quite natural to expect a degree of ‘normalization’ – that is a rise in temperature. Thus, for example, Schurer’s extra two tenths of warming might be the result of natural rather than anthropogenic causes.

The case for retaining the conventional pre-industrial baseline of 1850-1900 as the start of global warming, is supported by two papers, written by Dr Carl-Friedrich Schleussner, head of climate science and impacts at Climate Analytics; Dr Joeri Rogelj, research scholar at the International Institute for Applied Systems Analysis (IIASA) in Austria; and Dr Matthias Mengel, a postdoctoral scholar at the Potsdam Institute for Climate Impact Research. 14 15)

Summary

  1. Both the UNFCCC and the IPCC seem to accept the 1850-1900 baseline as being representative of “pre-industrial” climate conditions, although neither has confirmed this explicitly.
  2. While a case can be made for using different baselines based on different periods, none appear to have a clear advantage over the 1850-1900 baseline.
  3. In other words, the answer to the question – when did global warming start? – is, when we started burning significant amounts of fossil fuels. That is to say, during the period 1750-1800. However, because precise temperature measurements were not taken until 1850, scientists can’t agree on a better starting point. So the default answer remains: global warming continues to be measured by reference to 1850-1900 baseline data.

References

  1. Brohan, P. & Kennedy, John & Harris, Ian & Tett, S. & Jones, P. (2005). “Uncertainty estimates in regional and global observed temperature changes: A new dataset from 1850.” (1) []
  2. A. L. Morton, A People’s History of England (1938) page 284. (2) []
  3. Eric Hobsbawm, Industry and Empire (1968) Weidenfeld and Nicholson. Page 63. (3) []
  4. Eric Hobsbawm, Industry and Empire (1968) Weidenfeld and Nicholson. Page 64. (4) []
  5. Abram, Nerilie & Mcgregor, Helen & Tierney, Jessica & Evans, Michael & McKay, Nicholas & Kaufman, Darrell & Thirumalai, Kaustubh & Martrat, Belen & Goosse, Hugues & Phipps, Steven & Steig, Eric & Kilbourne, Hali & Saenger, Casey & Zinke, Jens & Leduc, Guillaume & Addison, Jason & Mortyn, P. & Seidenkrantz, Marit-Solveig & Sicre, Marie-Alexandrine & Von Gunten, Lucien. (2016). “Early onset of industrial-era warming across the oceans and continents.” Nature. 545. (5) []
  6. The Globe Is Already Above 1°C, on Its Way to 1.5°C. Climate Central. October 9, 2018. “Human activities have already warmed the planet about 1°C (1.8°F) since the pre-industrial era, defined by the IPCC as the latter half of the 19th century.” (6) []
  7. 2016: one of the warmest two years on record.” UK Met Office. Wed 18 Jan 2017. (7) []
  8. Importance of the pre-industrial baseline for likelihood of exceeding Paris goals.” Andrew P. Schurer, Michael E. Mann, Ed Hawkins, Simon F. B. Tett & Gabriele C. Hegerl. Nature Climate Change. Volume 7, pages 563–567 (2017) (8) []
  9. Emission budgets and pathways consistent with limiting warming to 1.5°C.” Richard J. Millar, Jan S. Fuglestvedt, Pierre Friedlingstein, Joeri Rogelj, Michael J. Grubb, H. Damon Matthews, Ragnhild B. Skeie, Piers M. Forster, David J. Frame & Myles R. Allen. Nature Geoscience Volume 10, pages 741–747 (2017) http://www.gci.org.uk/Documents/Myles_Allen.pdf – See also: (9) []
  10. Estimating Changes in Global Temperature since the Preindustrial Period.” Ed Hawkins, Pablo Ortega, Emma Suckling. Bulletin of the American Meteorological Society. Volume 98 No. 9. pp.1841–1856. September 2017. (10) []
  11. Reconstructing Earth’s surface temperature over the past 2000 years: the science behind the headlines.” Jason E. Smerdon, Henry N. Pollack. WIREs Climate Change 7:746–771. (2016) (11) []
  12. “Climate scientists debate a flaw in the Paris climate agreement.” Skepticalscience.com/ 29 March 2018. (12) []
  13. “Arctic Warming Twice as Fast as Rest of World.” Sid Perkins. American Association for the Advancement of Science (AAAS) Aug. 6, 2013. (13) []
  14. Don’t shift the goalposts of Paris Agreement’s temperature limits.” Dr Carl-Friedrich Schleussner, Dr Joeri Rogelj, Dr Matthias Mengel. Carbon Brief. 22 May, 2018. (14) []
  15. Global mean temperature indicators linked to warming levels avoiding climate risks.” Peter Pfleiderer, Carl-Friedrich Schleussner, Matthias Mengel, Joeri Rogelj. Environmental Research Letters, Volume 13, Number 6. Published 1 June 2018. (15[]
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