Climate Change, Week 3

Our climate has been subject to dramatic change over the last 150 years, we know this due to observing many variables in the climate system such as recording temperature. This is not just due to natural variations in the climate system, but also due to anthropogenic emissions of greenhouse gasses like carbon dioxide.

I am currently studying an online course on Climate Change from the University of Exeter, facilitated by Future Learn. Future Learn offers a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life. Oh and did I mention it is completely free? I recommend them, if you have a thirst for learning, you should check them out.


Key Lessons

Based on the end of week quiz (my results were 14 out of 15, or 93%).

  1. Recent increases in circumpolar wind strength around Antarctica, and changes in ocean circulation, have led to an increase in sea ice extent.
  2. The current atmosphere concentration of carbon dioxide in parts per million is 400ppm.
  3. The USA has the highest carbon emissions per capita.
  4. The deep ocean is the largest carbon store on the planet.
  5. The ice albedo feedback amplifies Arctic warming since ice has a higher albedo than land or water surfaces. Therefore, as Arctic ice cover decreases, the reflectivity of Earth’s surface decreases, more incoming solar radiation is absorbed by the surface, and the surface warms.

Signs of Climate Change

The global average temperature has increased dramatically over the 20th century to present day, the most recent decade being the warmest on record. The Arctic polar region has seen some of the highest temperature rises, since 1980 the surface area of Arctic sea ice fluctuates between four million and one and a half million square kilometres.

Since 1880 there has been a steady increase in sea levels. Around half of this rise is due to thermal expansion, the other half is due to the melting of land based ice from glaciers and the ice sheets around Greenland. Temperatures in Antarctica are cooler therefore ice is not melting here and does not contribute to the rise in sea levels. Melting sea ice does not contribute to the rise in sea levels since floating ice has already displaced the same volume of water as it would have if it were liquid.

Scientists use thermometers shielded by Stevenson screens, which negate the effects of direct radiation and rainfall. Meteorological temperatures are always measured in the shade, it is these temperatures that weather forecasters predict.


Our Changing Carbon Cycle

Our climate has been subject to dramatic change over the last 150 years, we know this due to observing many variables in the climate system such as recording temperature. This is not just due to natural variations in the climate system, but also due to anthropogenic emissions of greenhouse gasses such as carbon dioxide.

Since James Watt harnessed the power of the first commercialised steam engines back in 1776, economic development has been driven by the burning of fossil fuels. This has resulted in a rise in greenhouse gas emissions, including carbon dioxide, one of the key gasses that form the warming blanket around our planet.

Of the CO2 emissions that humans are directly responsible for, 90% comes from the burning of fossil fuels in developed countries such as the United States and Great Britain (though emerging economies such as India and China are beginning to play a major role), the remaining 10% comes from deforestation in countries such as Brazil and Indonesia.

10 petagrams of CO2 are released into the atmosphere every year due to human activities, however the atmospheric increase of CO2 is only 4.5 petagrams per year, 5.5 petagrams are absorbed by carbon sinks. The deep ocean is one of the largest carbon sinks on the planet. On land, more carbon dioxide in the atmosphere results in an increase in photosynthesis, which in turn results in more plant growth and the expansion of carbon sinks in the form of forests. Without these land sinks, the amount of CO2 in the atmosphere would be much higher. This is why deforestation is a serious threat to the global climate.

In 2013, the Mauna Loa observatory in Hawaii recorded a concentration of atmospheric CO2 of 400ppm, a value last seen over a million years ago.


Further Reading

Climate Indicators (Met Office)
http://www.metoffice.gov.uk/research/monitoring/climate

Extreme Events and Anomalies (Climate)
http://www.climate.gov/news-features/featured-images/state-climate-extreme-events

Arctic Sea Ice Shatters Previous Low Records (National Snow and Ice Data Center)
http://nsidc.org/news/newsroom/20121002_MinimumPR.html

Climate Change Viewer (United States Geological Survey)
http://regclim.coas.oregonstate.edu/visualization/gccv/cmip5-global-climate-change-viewer/index.html

Human Induced Climate Change (American Geophysical Union)
http://sciencepolicy.agu.org/files/2013/07/AGU-Climate-Change-Position-Statement_August-2013.pdf

Carbon Dioxide Emissions (The World Bank)
http://data.worldbank.org/indicator/EN.ATM.CO2E.KT/countries/CN-GB-US?display=graph