Chapter 19 Flashcards
What property of greenhouse gases allows them to absorb infrared radiation and thus trap heat within the atmosphere?
The greenhouse gases (GHG) vibrate at frequencies that are similar to those of infrared (IR) radiation. When IR radiation impinges on a GHG molecule, the molecule’s vibrational energy is enhanced and the radiation energy is converted into heat, which is trapped within the atmosphere.
Explain why the emission of CO2 from fossil fuel use is a climate forcing, while the solubility of CO2 in seawater is a climate feedback.
The combustion of fossil fuels releases CO2 that was previously stored in the crust. The resulting increase in atmospheric CO2 leads to a temperature increase. As the temperature increases, the solubility of CO2 in the ocean decreases and additional CO2 is released by the ocean, resulting in even higher atmospheric CO2 levels and higher temperatures.
Explain how the positioning of Gondwana at the South Pole contributed to glaciation during the Paleozoic.
Gondwana was situated over the South Pole for much of the Paleozoic and became glaciated during the Ordovician (Andean-Saharan Glaciation) and again during the Permian (Karoo Glaciation). These glaciations cooled the entire planet during these periods.
Most volcanic eruptions lead to short-term cooling, but long-term sustained volcanism can lead to warming. Describe the mechanisms for these two different consequences.
From a climate perspective, the two important volcanic gases are SO2 and CO2. SO2 is converted to sulphate aerosols which block sunlight and can lead to short-term cooling (years). CO2 can lead to warming, but only in situations where there is an elevated level of volcanism over at least thousands of years.
Using the orbital information on eccentricity, tilt, and precession, we could calculate variations in insolation for any latitude on Earth and for any month of the year. Why is it useful to choose the latitude of 65° as opposed to something like 30°? Why north instead of south? Why July instead of January?
We use 65° for estimating the glaciation potential of orbital variations because glaciers are most likely to form at high latitudes. We use 65° N rather than 65° S because for more than 50 million years the continents have been concentrated in the northern hemisphere. We use July instead of January because for glaciers to grow it’s more important to have cool summers than cold winters.
If the major currents in the oceans were to slow down or stop, how would that affect the distribution of heat on Earth, and what effect might that have on glaciation?
If the major currents in the oceans were to slow down or stop, the tropics would get hotter and the high-latitude areas would get colder, leading to expansion of glaciers and sea ice. The various feedbacks (e.g., higher albedo because of increased ice cover) would result in an overall cooler climate.
Explain the climate implications of the melting and breakdown of permafrost.
The main climate implication of the melting and breakdown of permafrost is that carbon that was trapped in the frozen ground will be released and then converted to CO2 and CH4, leading to more warming.
Much of the warming of the Paleocene-Eocene thermal maximum is thought to have been caused by the release of CH4 from sea-floor methane hydrates. Describe what must have happened before this could take place.
Sea-floor methane hydrates are stable because the deep ocean water is cold. In order for the hydrates to become unstable, warmth from the upper layers of the ocean has to be transferred to depth.
Burning fossil fuels emits CO2 to the atmosphere via reactions like this one: CH4 + O2 —-> CO2 + 2H2O. Describe some of the other ways that our extraction, transportation, and use of fossil fuels impact the climate.
A significant part of our GHG emissions take place during because of the (formerly) intentional and (presently) unavoidable release of natural gas (CH4) during the extraction of oil and gas. Some is lost during transportation — for example when pipelines leak — and some is consumed during transportation — for example to pressurize pipelines or to power tanker trains. GHGs are also leaked to the atmosphere during the routine refuelling and operation of motor vehicles.
Explain why, even if we could stop our impact on the climate tomorrow, we would still be facing between 1 and 2 m of additional sea-level rise.
The rise of sea level results from a combination of melting glaciers and thermal expansion of the ocean water. Both of these large systems are slow to respond to the warming climate. For example it takes a long time for warm surface water to be transferred to depth in the ocean or for heat to be transferred to depth in a glacier. Even if we stabilized the GHG levels in the atmosphere today, the climate would continue to warm for approximately another 100 years, and sea level would continue to rise for much longer than that.
How is the West Nile virus spread into Canada from the United States is related to climate change.
West Nile virus is carried by birds and is transmitted to humans by certain species of mosquitoes. The range and abundance of those mosquitoes is partly controlled by climate change, especially by warm winters. Sufficiently warm winters are increasingly common in the northern United States and southern Canada.
