A Habitat for Humanity

The atmosphere is changing. What is causing it – and what comes next?

planet is undergoing unexpected and complicated – but understandable – changes. Sunlight penetrating the Earth’s atmosphere is being trapped, and the world is storing heat energy more than it used to. Why is this change occurring? It is primarily caused by rising levels of several greenhouse gases – primarily carbon dioxide (CO2), followed by methane, which are part of the atmosphere shrouding the planet. The more of these gases (and water vapour) are in the atmosphere, the more efficiently the sun’s heat is captured.

These gases are important parts of biological systems. In fact, you – and all of the other animals on the planet – are releasing CO2 with every exhalation. We breathe in oxygen to allow us to burn sugars within our cells, and these are broken down into water and CO2 molecules. Each CO2 molecule is comprised of one carbon atom bound to two oxygen atoms, whereas water (H2O) is two hydrogen atoms bound to one oxygen atom.

Mirroring this process, but not necessarily balancing it, is the collection of CO2 by plants. Powered by sunlight, plants collect and combine CO2 with water to create the very mass of life. This includes the sugars that we break down to fuel our lives. Your body, the blades of grass, the wood of the forests, and almost all other living things are formed from that which is produced by green plants during photosynthesis.

Understanding the flow of carbon atoms through the planet is essential to understanding our changing atmosphere. Carbon is released into the atmosphere from biomass when it is broken down by fire or decomposition. You could think of our

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cells’ digestion of food as tiny biological ovens burning sugar. Similarly, carbon is released from biomass during forest fires or when it is broken down by fungus or other organisms.

However, the amount of carbon that is mobile within the atmosphere is only a fraction of what is actually on the planet. The element of carbon combines with other atoms to form different compounds, and only a small portion of the planet’s carbon is in the atmosphere as CO2.

More than half of the Earth’s carbon is present in rocks, such as limestone (bound to calcium and oxygen) or sandstone (primarily silicon). About a quarter is stored in the Earth’s oceans, and a miniscule portion travels into space by way of astronautics or meteors. The long and the short of it is that the rapid changes to Earth’s climate are primarily a story of vegetation clearing and the discovery of fossil energy.

The fossils and the forests

Ancient fossilised carbons are the critical piece to the puzzle: They underpin our modern civilisation and have granted us incredible reserves of energy. These fossil fuels – coal, oil, and natural gas – are the stored biomass or outgassing of biological material that has somehow been encapsulated on a vast scale. We dig them up, burn them, and release them into the atmosphere where they act as greenhouse gases. Overall, there is probably 20 times as much carbon stored as fossil fuels than there is living plant matter on Earth. These ancient organic materials have been housed in the rocks of the Earth for millions of years. In some forms, such as coal, you can clearly identify the leaves of plants that have accumulated into coal beds.

As these materials have been brought into furnaces to power engines, and into laboratories to create new compounds such as plastic, we have extracted the energy to build the manmade world around us. When these energies are used to clear forests and drain swamps, the carbon stored in organic matter begins to decompose, or is burnt, and it finds its way into the atmosphere. That, in a nutshell, is the foundation of the current crisis.

Past changes

There is a clear correlation between levels of CO2 in the atmosphere and the fluctuations in temperature of the planet. The Earth has experienced periods of great cold and great heat in its geological past, but it has been relatively stable for almost two million years.

There is a clear correlation between levels of CO2 in the atmosphere and the fluctuations in temperature of the planet

The climate of the last 1,000 years, and prior to the wide-scale burning of fossil fuels in the 1800s during the Industrial Revolution, has been part of a natural warming period after the most recent Ice Age.

Over the last half a million years, CO2 has shifted between 180 and 280 parts per million. Since 1950, primarily due to the burning of fossil fuels, it has skyrocketed to just over 400 parts per million, and it is not levelling out.

If this continues, we will experience a hotter climate in the years to come. We will need to find ways to either store CO2, or mitigate the greenhouse effect to avoid this uncertain, and increasingly ominous, future.

The discovery

Understanding global climate gases is built upon upon careful measurements and experimentation across disciplines including meteorology, chemistry, geology, astronomy, oceanography, botany, engineering, and physics. The Swiss naturalist de Saussure’s 1767 experiment with solar ovens led to Fourier’s 1824 realisation that the Earth could warm by sunlight’s heat energy failing to reflect back into space, developing further to produce Arrhenius’s 1859 calculations of climate change based on atmospheric gases.

Precision measurement of atmospheric CO2 began in 1958 on the peak of the Hawaiian volcano Mauna Loa; 100,000 years

of worldwide energy-related CO2 emissions, compared to

17 percent in 1990 Several tens of billions of dollars will be needed annually to help developing countries transition to low-carbon and climate-resilient economies, with USD40 billion annually for adaptation in Asia and the Pacific alone 20 million Bangladeshis would be displaced by a one metre rise in sea level by 2050 More than 60 percent of the region’s population works in agriculture, fisheries, and forestry, which are the sectors most at-risk to climate change

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