3. Reversing the rise

Stopping emissions. Even if all \(CO_{2}\) emissions stopped today, it would take over 1,000 years for sea level and surface temperatures to return to pre-industrial levels. – jsu

Representative Concentration Pathways. In order to estimate future climate impacts, we need to consider several possible greenhouse gas scenarios, called RCPs. http://en.wikipedia.org/wiki/Representative_Concentration_Pathways – cvh

In order to make one of the lowest two RCPs above (purple or green) occur, what must happen to EMISSIONS of greenhouse gases? – cvh
A.	Greenhouse gas emissions must decrease.
B.	Greenhouse gas emissions must increase.
C.	Greenhouse gas emissions must stay about the same.

→ Answer: (A)

Question. Draw it: Make a new card with your own drawing explaining your answer. Use an analogy if it helps: e.g., if the amount of greenhouse gas in the atmosphere is like the amount of water in a bathtub with the drain a little bit open, how do you adjust the water flow (emissions) to decrease or keep the water level? – cvh

– cvh

http://www.epa.gov/climatechange/science/causes.html – cvh

The point of no return. Since the early 20th century, land and ocean temperatures have risen to about \(0.7^{o} C\) above baseline levels. Carbon dioxide levels are now at 400 ppm. If we go above 450 ppm, scientists project that we will get to \(2^{o}C\) by the end of the century, the maximum "safe" level. Beyond that, forests can burn down and glaciers & ice sheets can melt in a way that will release further greenhouse gases into the atmosphere, causing runaway and irreversible changes to our climate. – jsu

[1]

Scenarios for different temperature rises. – jsu

Question. what do you guys think about the effectiveness of cap and trade in California? – Richard

Question. What should we do first? what could each of us do tomorrow? – Richard

Resulting climate changes from RCPs. Summary for Policymakers, Climate Change 2013, Fifth Assessment Report of the IPCC. – cvh

[2]

IPCC reports that the world is headed for irreversible climate changes. – jsu

The importance of fossil fuels. Oil is an inexpensive and abundant source of energy, whose extraction and use has lifted billions of people out of poverty. Along with natural gas, it makes up over half of all energy used in the world; it powers nearly all transportation. There is a moral case that developing countries should be able to use this resource to increase their wealth in the same way developed countries have. Yet dire consequences will follow if this occurs. Developing countries will also be disproportionately affected by the impact of climate change. This tension is a fundamental one, and not easily resolved. – jsu

[3]

An excellent article on the importance of oil to world development. – jsu

[4]

Poor countries need access to fossil fuels – jsu

Alternative fuels. No technology can feasibly replace fossil fuels as a source of energy over the next century. It is clear though that the world will move to non-emitting technologies, such as solar, nuclear, and wind power. Furthermore, these technologies all produce electricity, which can only be transiently stored in small quantities. Hydrocarbons (like the oil in our car, and the fat in our body!) are excellent at storing energy -- but they release \(CO_{2}\) when burned. We will need to solve both the energy problem, and the energy storage problem. – jsu

Geoengineering strategies. Scientists have proposed strategies to rapidly combat the effects of global warming. For example, sulfate particles could be injected into the atmosphere. These would reflect sunlight and cause the Earth to cool down. Another possibility would be to seed the ocean with iron fillings. This would cause algae to proliferate, drawing \(CO_{2}\) out from the atmosphere. Such strategies are likely to be effective, but their ultimate consqeuences are not known. Unilateral and direct efforts to change climate are understandably controversial. – jsu

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