The Basic Science of Climate Change

When fuels like coal or petroleum are burned or extracted, they release CO2 and other heat-trapping greenhouse gases. Currently, CO2 levels are around 400ppm (parts per million). That’s 40% more than the highest natural levels over the last 800,000 years. The extra CO2 in the air is also due to worldwide deforestation. Clearing forests releases large amounts of CO2, and plants and trees use CO2 to grow. Deforestation means there aren’t as many trees to absorb the extra CO2, thus the CO2 stays in the atmosphere, trapping more heat. Over the past 50 years the average global temperature has increased at the fastest rate in recorded history; the 10 hottest years on record have all occurred since 1990. Scientists agree that if we don’t curb global warming emissions, average U.S. temperatures could be 3 to 9 degrees higher by the end of the century.

The Dangers of Global Warming

There are serious consequences already happening because of global warming, and climate scientists predict there will be more to come. Here are some of the dangerous weather changes caused by global warming:

Melting glaciers, early snowmelt and severe droughts will cause more dramatic water shortages in the American West. Rising sea levels will lead to coastal flooding on the Eastern seaboard, in Florida, and in other areas, such as the Gulf of Mexico. Warmer sea surface temperatures will fuel more intense hurricanes in the southeastern Atlantic and Gulf coasts. Forests, farms and cities will face troublesome new pests and more mosquito-borne diseases. Disruption of habitats such as coral reefs and alpine meadows could drive many plant and animal species to extinction.

The World’s Response

In 1992, countries joined an international treaty, the United Nations Framework Convention on Climate Change (UNFCCC), to cooperatively consider what they could do to limit average global temperature increases and the resulting climate change, and to cope with whatever impacts were, by then, inevitable. By 1995, countries realized that emission reductions provisions in the Convention were inadequate. They launched negotiations to strengthen the global response to climate change, and, two years later, adopted the Kyoto Protocol. The Kyoto Protocol legally binds developed countries to emission reduction targets. The Protocol’s first commitment period started in 2008 and ended in 2012. The second commitment period began in 2013 and will end in 2020. There are now 195 Parties to the Convention and 192 Parties to the Kyoto Protocol.

Why We Use Climate Models

Global climate models (GCMs) use math to describe how the atmosphere, oceans, land, living beings, ice, and sun affect the earth’s climate. Climate scientists use GCMs to better understand how global changes, such as increasing greenhouse gases, or decreasing Artic sea ice, will affect the earth. The models are used to look hundreds of years into the future, so that we can predict how our planet’s climate will change. At the National Center for Atmospheric Research (NCAR), researchers work with complex models of the Earth’s climate system. Their Community Climate System Model is so complex that it requires about three trillion math calculations to simulate a single day on the earth. It can take thousands of hours for the supercomputer to run the model. The model output, typically many gigabytes large, is analyzed by researchers and compared with other model results.


The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. The IPCC is a scientific body under the auspices of the United Nations (UN). It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It does not conduct any research nor does it monitor climate related data or parameters. Thousands of scientists from all over the world contribute to the work of the IPCC on a voluntary basis. By endorsing the IPCC reports, governments acknowledge the authority of their scientific content. The work of the organization is therefore policy-relevant and yet policy-neutral, never policy-prescriptive.

What is a Climate Summit?

Since the UNFCCC entered into force, the parties have been meeting annually in Conferences of the Parties (COP), otherwise known as climate summits, to assess progress in dealing with climate change, and to negotiate the Kyoto Protocol to establish legally binding obligations for developed countries to reduce their greenhouse gas emissions. A key element of the UNFCCC is that parties should act to protect the climate system “on the basis of equality and in accordance with their common but differentiated responsibilities and respective capabilities.”

A Brief History of COPs

Here are just a few of the important decisions and resolutions that have come out of past UN COPs:

COP 4 (Buenos Aires, 1998) – The Buenos Aires Plan of Action was adopted, which established deadlines for finalizing the outstanding details of the Kyoto Protocol so that the agreement would be fully operational by 2000. In addition, the Plan of Action discussed work on transferring climate-friendly technologies to developing countries and addressed the special needs and concerns of countries affected by global warming and by the economic implications of response measures.

COP 9 (Milan, 2003) - New emission reporting guidelines based on the good-practice guidance provided by the IPCC were adopted to provide a sound and reliable foundation for reporting on changes in carbon concentrations resulting from land-use changes and forestry. Another major advance was the agreement on the modalities and scope for carbon absorbing forest-management projects in the clean development mechanism (CDM). 

COP 13 (Bali, 2007) - COP 13 adopted the Bali Road Map, as a two-year process towards a strengthened international climate change agreement. The Bali Road Map includes The Bali Action Plan, which is divided into five main categories: shared vision, mitigation, adaptation, technology and financing. The shared vision refers to a long-term vision for action on climate change, including a long-term goal for emission reductions.

COP 15 (Copenhagen, 2009) – The Copenhagen Climate Change Conference raised climate change policy to the highest political level, with close to 115 world leaders attending the high-level segment. It produced the Copenhagen Accord, which was supported by a majority of countries. This included agreement on the long-term goal of limiting the maximum global average temperature increase to no more than 2 degrees Celsius about pre-industrial levels, subject to a review in 2015. A number of developing countries agreed to communicate their efforts to limit greenhouse gas emissions every two years.

Further Reading

Climate Change 101 was compiled from the following list of sources:

What is Global Warming

What is a Climate Model

Background on the UNFCCC: The international response to climate change

IPCC: Organization

Climate Leaders

A Brief Overview of Decisions


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