Antarctica and global climate change

A changing climate

The Earth’s climate is always changing, but the changes are usually very slow – typically taking hundreds to thousands of years. Natural processes such as variations in the Earth’s orbit, solar energy distribution and volcanic eruptions can influence the climate.

The greenhouse effect

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What happens to incoming solar radiation?

6% is scattered by the atmosphere, 20% is absorbed by the atmosphere and clouds, 20% is reflected by clouds, 49% is absorbed by the Earth's surface and 5% is reflected by the Earth's surface.

Rights: The University of Waikato Te Whare Wānanga o Waikato

Over millions of years, the Earth has alternated between warm and cold periods, but the climate has been fairly stable over the last 10,000 years. This stability has allowed a large variety of different ecosystems (and humans) to establish and flourish.

Human activities in the last century have had an effect on this natural climate balance. Greenhouse gases (carbon dioxide, water vapour, methane and other gases) act like a blanket and cause the Earth to warm. Even small changes in the global average temperature can lead to large shifts in climate and weather.

Antarctica and global climate change

Antarctica is an ideal location to study local-to-global scale climate change. The low diversity of life in the Dry Valleys allows scientists to study it in great detail – including the effects of small climate changes. Scientists think that, once they understand how things work in Antarctica, they can use this knowledge to make predictions about the impacts of climate change elsewhere.

Part of me thinks, ‘Why are we up in the Dry Valleys? If no one ever goes there, why do we need to know anything about them?’ And then you discover that, because it’s such a microbiologically unique environment, it is pretty much the perfect place to look for early indicators of climate change and what the implications of that might be.

Nigel Latta

Ice core showing annual rings

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This is an ice core showing annual rings. The oldest ice ever retrieved was about 950 thousand years old.

Rights: Dr Katja Riedel

Antarctica also acts like an archive for ancient history. Small amounts of air get trapped in ice and can reveal climate information from the past. Scientists have charted greenhouse gas levels from as far back as 800,00 years. Ice core data shows that temperatures were warmer when there were more greenhouse gases in the atmosphere and vice versa.

Fossil evidence goes back even further. It shows that, around 45 million years ago, Antarctica resembled a South Island bush ecosystem, with trees, amphibians, insects and fish. Over 10 million years, the climate cooled and the forests were replaced with ice and scrubby grasslands – similar to those found along the central North Island’s Desert Road. Further cooling meant that Antarctica became the ice-covered continent it is today.

Earth’s climate has therefore always changed, but it’s the influence of human impacts that is now causing enormous international concern and activity.

Potential climate change impacts on New Zealand

Climate scientists expect the Earth’s average temperature to increase by between 1°C and 6°C this century. In New Zealand, the Ministry for the Environment predicts the average temperature will rise by about 2°C. While it does not sound like much, warmer temperatures may cause:

• more frequent extreme weather events such as droughts and floods

• a need to change land use activities due to changes in rainfall patterns

• sea level rises and coastal erosion

• changes to South Island water flows as snowlines and glaciers retreat

• native ecosystems to be affected by an increase in pest species

Acknowledgments

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Rights: TVNZ, Razor Films, NZ On Air