History of the greenhouse effect and global warming

Svante Arrhenius (1859-1927) was a Swedish scientist that was the first to claim in 1896 that fossil fuel combustion may eventually result in enhanced global warming. He proposed a relation between atmospheric carbon dioxide concentrations and temperature. He found that the average surface temperature of the earth is about 15^oC because of the infrared absorption capacity of water vapor and carbon dioxide. This is called the natural greenhouse effect. Arrhenius suggested a doubling of the CO₂ concentration would lead to a 5^oC temperature rise. He and Thomas Chamberlin calculated that human activities could warm the earth by adding carbon dioxide to the atmosphere. This research was a by-product of research of whether carbon dioxide would explain the causes of the great Ice Ages. This was not actually verified until 1987.

After the discoveries of Arrhenius and Chamberlin the topic was forgotten for a very long time. At that time it was thought than human influences were insignificant compared to natural forces, such as solar activity and ocean circulation. It was also believed that the oceans were such great carbon sinks that they would automatically cancel out our pollution. Water vapor was seen as a much more influential greenhouse gas.

In the 1940's there were developments in infrared spectroscopy for measuring long-wave radiation. At that time it was proven that increasing the amount of atmospheric carbon dioxide resulted in more absorption of infrared radiation. It was also discovered that water vapor absorbed totally different types of radiation than carbon dioxide. Gilbert Plass summarized these results in 1955. He concluded that adding more carbon dioxide to the atmosphere would intercept infrared radiation that is otherwise lost to space, warming the earth.

The argument that the oceans would absorb most carbon dioxide was still intact. However, in the 1950's evidence was found that carbon dioxide has an atmospheric lifetime of approximately 10 years. Moreover, it was not yet known what would happen to a carbon dioxide molecule after it would eventually dissolve in the ocean. Perhaps the carbon dioxide holding capacity of oceans was limited, or carbon dioxide could be transferred back to the atmosphere after some time. Research showed that the ocean could never be the complete sink for all atmospheric CO₂. It is thought that only nearly a third of anthropogenic CO₂ is absorbed by oceans.

In the late 1950's and early 1960's Charles Keeling used the most modern technologies available to produce concentration curves for atmospheric CO₂ in Antarctica and Mauna Loa. These curves have become one of the major icons of global warming. The curves showed a downward trend of global annual temperature from the 1940's to the 1970's. At the same time ocean sediment research showed that there had been no less than 32 cold-warm cycles in the last 2,5 million years, rather than only 4. Therefore, fear began to develop that a new ice age might be near. The media and many scientists ignored scientific data of the 1950's and 1960's in favor of global cooling.

In the 1980's, finally, the global annual mean temperature curve started to rise. People began to question the theory of an upcoming new ice age. In the late 1980's the curve began to increase so steeply that the global warming theory began to win terrain fast. Environmental NGO's (Non-Governmental Organizations) started to advocate global environmental protection to prevent further global warming. The press also gained an interest in global warming. It soon became a hot news topic that was repeated on a global scale. Pictures of smoke stags were put next to pictures of melting ice caps and flood events. A complete media circus evolved that convinced many people we are on the edge of a significant climate change that has many negative impacts on our world today. Stephen Schneider had first predicted global warming in 1976. This made him one of the world's leading global warming experts.

In 1988 it was finally acknowledged that climate was warmer than any period since 1880. The greenhouse effect theory was named and Intergovernmental Panel on Climate Change (IPCC) was founded by the United Nations Environmental Programme and the World Meteorological Organization. This organization tries to predict the impact of the greenhouse effect according to existing climate models and literature information. The Panel consists of more than 2500 scientific and technical experts from more than 60 countries all over the world. The scientists are from widely divergent research fields including climatology, ecology, economics, medicine, and oceanography. The IPCC is referred to as the largest peer-reviewed scientific cooperation project in history. The IPCC released climate change reports in 1992 and 1996, and the latest revised version in 2001.

In the 1990's scientists started to question the greenhouse effect theory, because of major uncertainties in the data sets and model outcomes. They protested the basis of the theory, which was data of global annual mean temperatures. They believed that the measurements were not carried out correctly and that data from oceans was missing. Cooling trends were not explained by the global warming data and satellites showed completely different temperature records from the initial ones. The idea began to grow that global warming models had overestimated the warming trend of the past 100 years. This caused the IPCC to review their initial data on global warming, but this did not make them reconsider whether the trend actually exists. We now know that 1998 was globally the warmest year on record, followed by 2002, 2003, 2001 and 1997. The 10 warmest years on record have all occurred since 1990.

The climate records of the IPCC are still contested by many other scientists, causing new research and frequent responses to skeptics by the IPCC. This global warming discussion is still continuing today and data is constantly checked and renewed. Models are also updated and adjusted to new discoveries and new theory.

So far not many measures have been taken to do something about climate change. This is largely caused by the major uncertainties still surrounding the theory. But climate change is also a global problem that is hard to solve by single countries. Therefore in 1998 the Kyoto Protocol was negotiated in Kyoto, Japan. It requires participating countries to reduce their anthropogenic greenhouse gas emissions (CO₂, CH₄, N₂O, HFCs, PFCs, and SF₆) by at least 5% below 1990 levels in the commitment period 2008 to 2012. The Kyoto Protocol was eventually signed in Bonn in 2001 by 186 countries. Several countries such as the United States and Australia have retreated.

From 1998 onwards the terminology on the greenhouse effect started to change as a result of media influences. The greenhouse effect as a term was used fewer and fewer and people started to refer to the theory as either global warming or climate change.