The Three Core Studies That Answered The Question of Climate Change

The Pioneering Study on Climate Change: The IPCC Report

We started witnessing manifestations of global warming and climate change in the 1990s. The first assessment report by the Inter-governmental Panel on Climate Change (IPCC) was published during this period. The IPCC report was the first-ever serious study on the topic. 

The naturally occurring greenhouse gas effect was identified for the first time and explained in this report. The report connected atmospheric emissions to human activity. The gases such as methane, carbon dioxide, chlorofluorocarbons, and nitrous oxide were pinpointed as the major greenhouse gases. The report concluded that the greenhouse effect would eventually lead to the warming of the earth’s atmosphere, resulting in drastic threats to sustainability.

The report called for major changes in human developmental activities to mitigate climate change. It warned unless these changes are affected, humanity will face unimaginable consequences. Carbon Dioxide was the major contributor to the greenhouse effect, with half of the global warming burden caused by it. This study also calculated the future projections of the greenhouse effect and predicted that the global mean temperature would rise by 0.3 degrees Celcius every decade, an unprecedented rise compared to the temperature variations of the last 100 centuries.

According to this report, the global mean sea level has risen by about 6 cm every decade. The reasons for this include the expansion of oceans caused by absorbing heat from the atmosphere and Glacier melting. This study predicted that sea levels would rise by 20 cm by 2030. The only positive conclusion that the report made was that humans can put a check on climate change. The study envisaged this as possible only if we commit ourselves to reducing greenhouse gas emissions by developing more sustainable models of development, industrial production, and living.

The Second Major Study on Climate Change

The next significant study on climate change was published in 1993. A team of scientists, including W. Dansgaard, S.J. Johnsen, H.B. Clausen, and D. Dahl-Densen, carried out this study titled, Evidence for general instability of past climate from a 250-KYR ice-core record. This study contradicted the preceding and pioneering IPCC study. It argued that climate change was not human-made. The authors also argued that the Holocene, the present geological epoch, like all other previous epochs, will or may witness an unstable climate, irrespective of what positive or negative acts we humans carry out concerning nature and the environment. 

This argument was presented after the researchers tabulated a comprehensive stable-isotope record of the Greenland Ice-core project summit ice core, an ice core in Greenland selected for study under a multinational European climate research project. Dansgaard and his colleagues also concluded that the interglacial period before the present one could also have experienced extreme climate change. Two types of climatic periods that occur intermittently comprise the geo-climatic history of Earth- glacial and interglacial periods. Glacials are what we call in our popular culture the Ice Ages. Interglacials are when the earth experiences a warm climate like the one we have now. 

The researchers concluded that the last interglacial period extended more than its expected time range due to drastic climate variations. They proposed that this happened because of the climate variations causing a delay in glacier melting.

We now live in another interglacial period. If what Dansgaard and his friends argued is correct, it is possible that big climate changes can occur in a short period, and there is nothing that we can do about it. This study took us to someplace that looked like a dead-end. 

This study took a proven scientific route to test whether climate change is natural or a problem induced by human activity. The method was simple- the ratios of oxygen isotopes in ice and the ocean beds were determined to see if these geological regions had endured any huge temperature variations in the history of Earth. 

In glacial epochs, the seas would be at freezing temperatures, and in such an environment, the 16O oxygen isotope in the sea bed would have evaporated fast. The result would be that the 18O oxygen isotope, which is heavier, will remain in the sea bed in greater concentrations. In interglacial periods, the reverse is the rule. These concentration differences get imprinted on the fossils of some sea organisms. By studying these fossils, one can understand which oxygen isotope persisted in which period and how warm or cold it was. Studying the oxygen isotopes, Dansgaard and his co-researchers argued that climate change is a natural phenomenon.

Though both studies mentioned above contradict each other, they agree that climate change is happening. The disagreement was on whether it is human-induced or natural. The answer to this question was important. If human activity has caused it, there is hope for reversing it.

The Third Study That Cleared the Doubts

A third study addressed this exact question in 1995. It was carried out by M. Patrick McCormick, Larry W. Thomason, and Charles R. Trepte. This research project studied the 1991 volcano eruption of Mount Pinatubo, which is situated in the Philippines. The study ventured to find answers by understanding how the aerosol and chemical particles from a volcano eruption interacted with the atmosphere.

They recorded that the aerosol and chemical particles from a volcano eruption move from one point in the atmosphere (the immediate atmosphere above the volcano), then circle the globe, and reach back to the same point in 22 days. This quick movement of the volcano residue in the atmosphere was a new phenomenon.

The quick atmospheric transference happens because of the warming effect that the volcano has on the atmosphere. The aerosols absorb infrared rays from the sun. This keeps the stratosphere warm for almost one year as the aerosols are trapped there. Gradually, when the aerosols migrate to the lowest strata of the atmosphere, the troposphere, this sphere begins to reflect more sunlight. This causes Earth to cool. Parallel to this, there always is a naturally occurring greenhouse warming effect. This is caused by the aerosols already in the atmosphere as they absorb infrared rays from the sun. The cooling effect was stronger than the warming effect in 1992. This happened because extra aerosols from the volcano eruption were present. Because of this, 1992 became the coolest year in many decades.

From the above, it becomes evident that extra aerosols emitted by human-induced pollution can have the same effect. This third study proved that our greenhouse gas emissions impact Earth's climate. This also proved ozone layer depletion is a phenomenon caused by human activity. What causes ozone depletion is the high concentration of chlorine in the atmosphere's lower stratum. Industrial pollution and greenhouse gas emissions are at the root of this. From the three studies discussed above, it is easy to factually conclude that there are human causes for global warming and climate change. There are natural causes, too. We need to realise this and do our part to mitigate global warming. 

References

Climate change: the intergovernmental panel on climate change scientific assessment – policymakers’ summary by Houghton, J.T., Jenkins, G.J., and Ephiraums, J.J., 1990.

Evidence for general instability of past climate from a 250-KYR ice-core record by Dansgaard, W. et al., Nature, 1993.

Atmospheric effects of the Mt. Pinatubo Eruption, McCormick, P.M., Thomason, L.W., and Trepte, C.R., Nature, 1993.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualised advice from a qualified professional.