The History of Climate Change
The planet and our knowledge of it are constantly changing. Today we all know the earth is a sphere, but a few centuries ago the shape of the planet was fiercely debated. Many people thought that the earth was flat, less than 10,000 years old and located at the centre of the universe. We now believe that the earth is a spinning globe part of a larger solar system in an even larger galaxy, and is approximately 4.6 billion years old. A lot can change in just a few centuries.
Climate Change, Nothing New
Climatic change is not new to our planet. Over the last few billion years the earth has witnessed tropical forests spread across entire continents, dinosaurs roam the landscape, ice sheets covering most of the Northern Hemisphere, and sea levels decrease by 100 meters! These processes are part of the planet's natural climatic variability. Unfortunately, many ecosystems and organisms suffer as these changes take place, while others thrive in the new environment .
Over the last 450,000 years, the earth has gone through several ice ages (global cooling) followed by warming periods (global warming) . These climatic changes have shaped the ecosystems that we see today. Animals and plants that live on the earth at present have evolved over a long period of time under pressures from their surrounding environment. While climates and habitats have always changed, the problem today for these organisms is that the changes are occurring faster than ever .
Since humans have been on this earth, we have influenced and changed the environment and the organisms around us . Although change is not new to the planet, rarely has it occur so quickly and dramatically . Evolution for most organisms is a slow process, and at the rate the climate is changing, there is little time for them to adapt.
Over the last two centuries, human activities have profoundly increased the amount of greenhouse gases in the atmosphere. Burning fossil fuels has released carbon dioxide into the air. Clearing forests for timber has removed plants that would otherwise take out carbon dioxide from the atmosphere . Bogs that store methane have been ploughed for development . Massive numbers of methane-producing livestock have been raised around the world . Humans have altered the atmosphere's delicate balance by creating and releasing large amounts of greenhouse gases, and we continue to do so today.
Warming on a global scale due to increased greenhouse gases has many impacts. Higher temperatures cause snow packs and ice sheets to melt, leading to rising sea levels . Increased temperatures on land can change vegetation coverage and forest communities . Animal and plant distributions are expected to shift as they attempt to stay within their thermal ranges . Temperate and equatorial species are predicted to move towards the poles, and habitats in the Arctic and Antarctic are expected to shrink . Greenhouse gases will also affect ocean chemistry. As the oceans absorb carbon dioxide, the water will become more acidic , affecting all living things in the marine environment – from small floating plankton to giant whales.
Just as past societies changed their beliefs on the idea that the earth is flat, so too must we change our behaviours in order to combat the global warming dilemma. Instead of keeping our heads buried in the sand, we must become aware of our impacts on the planet and start taking action now to reverse them. It's a big step. But, as we have come to see, a lot can change in just a few centuries.
1. Overpeck, J.T. and J.E. Cole, Abrupt change in Earth's climate system. Annual Review of Environmental Resources, 2006. 31 : p. 1-31.
2. Brook, E.J., Tiny Bubbles Tell All. Science, 2005. 310 : p. 1285-1287.
3. Ruddiman, W.E., How did humans first alter global climate. Scientific American, 2002. 292 (3).
4. Skutsch, M., et al., Clearing the way for reducing emissions from tropical deforestation. Environmental Science and Policy, 2007. 10 : p. 322-334.
5. Tarnocai, C., The effect of climate change on carbon in Canadian peatlands. Global and Planetary Change, 2006. 53 : p. 222-232.
6. DeRamus, A.H., et al., Methane emissions of beef cattle on forages: Efficiency of grazing management systems. Journal of Environmental Quality, 2003. 32 : p. 269-277.
7. Alley, R., et al., Climate Change 2007: The Physical Science Basis, Summary for Policymakers. 2007, Intergovernmental Panel on Climate Change. p. 18.
8. Parmesan, C., Ecological and Evolutionary responses to recent climate change. Review of Ecological and Evolution Systems, 2006. 37 : p. 637-669.
9. Harley, C.D., et al., The impacts of climate change in coastal marine systems. Ecology Letters, 2006. 9 : p. 228-241.
10. Cicerone, R., et al., The ocean in a high CO2 world. Earth and Ocean Science, 2004. 85 (37): p. 351-353.