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Is Climate Change Natural or Human Made? The Three Studies That Answered This Question

Updated on April 14, 2024
Deepa damodaran profile image

Deepa is a freelance researcher and journalist. She writes and makes documentaries and videos.

The Pioneering Study on Climate Change

If global warming and climate change cause even a 5 % increase in the surface temperature of Earth, all life could get wiped out from our lovely planet. The rising temperatures have become a phenomenon that we are used to living with.

In the 1990s, we started seeing evident manifestations of global warming and climate change. The first assessment report by Inter-Governmental Panel on Climate Change was published during this period and this became 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. It was concluded that the greenhouse effect would eventually lead to the warming of the earth’s atmosphere resulting in drastic threats to its sustainability.

The report called for major changes in human developmental activities to assuage climate change and warned that unless these changes are affected, humanity will be facing 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 will rise by 0.3 degrees Celcius every decade. This was an unprecedented rise when compared to the temperature variations of the last 100 centuries.

The global mean sea level is rising by about 6 cm every decade, according to this report. The expansion of oceans caused by absorbing heat from the atmosphere and Glacier melting are cited as the reasons for this. 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. This is possible only if we are committing ourselves to reduce greenhouse gas emissions by developing more sustainable models of development, industrial production, and living.

The Argument that Climate Change is Not Human Made

The next major 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 previous pioneering study and argued that climate change was not human-made. They 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 with respect to nature and the environment. This argument was made 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 argued that the interglacial period that happened in history before the present one also could have experienced extreme climate changes. The geological history of the earth is divided into two types of periods, namely, the glacial and the interglacial. Glacials are what we call in our popular culture, the ice ages. Interglacials are when the earth experiences a warm climate like what we have now. The researchers concluded that owing to the drastic climate variations in the last interglacial, the period itself got extended. This happened because the climate variations caused a delay in the melting of glaciers.

We now live in another interglacial period. If what Dansgaard and his friends argued is correct, it is possible that big changes in climate can occur in a short span of time and there is nothing that we can do about it. As this looks like a dead-end, let us examine one more important study that was carried out on climate change

The Study That Proved The Green House Gas Emissions From Human Activity Can Worsen Climate Change

There is a method of testing climate change. This is the method by which the ratio of oxygen isotopes in ice as well as in the ocean beds is determined to find out if these geological regions had endured any huge temperature variations in the history of the earth. The ratio changes indicate temperature variations.

In glacial epochs, the seas would be at freezing temperatures and in such an environment, the 16O oxygen isotope in the sea bed evaporates fast. The result is 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 find out which oxygen isotope persisted and how warm or cold it was. It was based on studying these oxygen isotopes that Dansgaard and his co-researchers argued that climate change was a natural phenomenon and not a human-made one.

Though both the studies mentioned above contradict each other, they both agree that climate change is happening. The only disagreement that remains is whether it is human-made or a natural phenomenon and also whether humans can reverse it.

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. What the study ventured to find out was the process of how the aerosol and chemical particles from the volcano eruption interacted with the atmosphere.

It was observed that these particles moved from one point in the atmosphere (which is the immediate atmosphere above the volcano), then circled the globe, and reached back to the exact same point in 22 days. The quick movement of the volcano residue in the atmosphere was a new phenomenon.

It was concluded that this type of atmospheric transference happens because of the warming effect that the volcano had on the atmosphere. The aerosols absorbed infrared rays from the sun. This kept the stratosphere of the atmosphere warm for almost one year as the aerosols were trapped there. Gradually when the aerosols migrated to the lowest strata of the atmosphere, namely, the troposphere, the troposphere began to reflect more sunlight and resulted in a cooling of the earth.

However, there was also a naturally occurring greenhouse warming effect. This was caused by the aerosols already present in the atmosphere absorbing infrared rays from the sun. The cooling effect was stronger than the warming effect in the year, 1992, because of the extra aerosols in the atmosphere owing to the volcano eruption. Because of this, 1992 became the coolest year in many decades. From the above phenomenon, it becomes evident that extra aerosols emitted by human-made pollution also can have the same effect.

The phenomenon discussed above was proof of the fact that the greenhouse gas emissions caused by humans can have an impact on the climate of the earth. This led to the conclusion that the depletion of the ozone layer above the atmosphere is a human-made phenomenon. The high concentration of chlorine in the lower stratum of the atmosphere is the cause of ozone depletion. This obviously is caused by industrial pollution and other greenhouse gas emissions.

What These Three Baseline Studies on Climate Change Prove

By analyzing the three studies discussed above, it is discernible that there are human-made reasons at play in global warming and climate change, as equally there are natural causes. We need to realise this and do our part to mitigate global warming. This is the only way in which can keep the earth inhabitable for our future generations.

More on this topic-


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. 1993. Published in Nature.

Atmospheric effects of the Mt. Pinatubo Eruption, McCormick, P.M., Thomason, L.W., and Trepte, C.R. 1995. Published in Nature.

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

© 2020 Deepa


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