Picture: NASA in the public domain
Unit 1: Climate change
Climate change is considered by many to be the world’s greatest problem (technically a context hazard); and so a chronic, large-scale threat to people. Uncertainty about its impact is inevitable as scientists struggle to make firm predictions. It is an unfair world in which the wealthiest countries have emitted most of the greenhouse gases and the poorest ones are most vulnerable to their impacts. This topic poses questions about the causes of global warming, its relationship to long-term climate change, and the direct and indirect impacts that result. It also considers some of the solutions, whether global or local, and the complexity of managing international concerns against a background of national and personal self-interest. It also provides suggestions for tackling a variety of global hazards.
What are the natural and human causes, impacts and responses to climate change?
Who is Milankovitch and what did theorise?Milankovitch was a Serbian astrophysicist who created a mathematical model for long-term climate change. His theory (the Milankovitch cycles) states that as the Earth travels through space around the sun, the cyclical variations in three elements of Earth-sun geometry combine to produce variations in the amount of solar energy that reaches Earth, these elements are:
The Milankovitch cycles can be seen in the long-term climate change pattern of the last 400 000 years, shown below in an UNEP graph from J.R Petit, J Jouzel., et al. Climate and atmospheric history of the past 420,000 years from the Vostok ice core in America, Nature 399, pg 429-436, 1999, available here.
Who is Milankovitch and what did theorise?Milankovitch was a Serbian astrophysicist who created a mathematical model for long-term climate change. His theory (the Milankovitch cycles) states that as the Earth travels through space around the sun, the cyclical variations in three elements of Earth-sun geometry combine to produce variations in the amount of solar energy that reaches Earth, these elements are:
- The variations in the Earth's orbital eccentricity - From circular to elliptical in a cycle that takes around 95 000 years. When the orbit is circular (highly elliptical), the amount of insolation received at the closest point (perihelion) would be up to 30 percent greater than at the furthest point (aphelion).
- Changes in obliquity - Changes in the angle that Earth's axis makes with the plane of Earth's orbit, as the axial tilt increases from 22 to 24.5 degrees over 40 000 years. The seasonal contrast increases so that winters are colder and summers are warmer across the globe.
- Precession - The change in the direction of the Earth's axis of rotation.
The Milankovitch cycles can be seen in the long-term climate change pattern of the last 400 000 years, shown below in an UNEP graph from J.R Petit, J Jouzel., et al. Climate and atmospheric history of the past 420,000 years from the Vostok ice core in America, Nature 399, pg 429-436, 1999, available here.
The Consensus project above, shows some useful animations explaining the enhanced greenhouse effect - link here.
The impact of climate change in America, shown below. Source: Public domain: White House
Africa is likely to be the continent which is hit hardest by climate change, despite contributing the least towards anthropogenic climate change. UNEP have written a report about the impacts on climate change here.The above map shows the climate hotspots in Africa, published in the Guardian - link here.
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Arctic temperatures are changing twice as fast as anywhere else in the world. This will impact on the fragile ecosystems, where temperature has been the most significant limiting factor for plant growth and therefore energy in the food web. The graph above was published in the Independent (link here) and shows how rapid climate change n the Arctic is taking place. Read the National Geographic article about warming in Hudson Bay.
Some commentators think that a warmer Arctic will be a good thing. Decide for yourself - find out more at the Oceans North and WWF Global websites.
Responses to climate change can occur on an Intergovernmental, national and local scale - watch some of these short YouTube clips to find out what different people are doing...
Some commentators think that a warmer Arctic will be a good thing. Decide for yourself - find out more at the Oceans North and WWF Global websites.
Responses to climate change can occur on an Intergovernmental, national and local scale - watch some of these short YouTube clips to find out what different people are doing...
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