Climate Change and Global Warming Questions and Answers

Answer: B

The option that is not mitigation is increased capacity of traditional power plants.

Traditional power plants burn coal, oil or gas, so adding to their capacity increases fossil fuel use and carbon dioxide emissions, the opposite of mitigation.

The other three reduce net emissions. Wind energy and photovoltaic cells generate electricity without burning fuel, replacing fossil generation, and afforestation draws carbon dioxide out of the air and stores it in trees and soil.

Answer: A

There will be increased mortality due to heat waves.

As average temperatures rise, heat waves become more frequent, intense and long, and heat stress kills the elderly, the sick, outdoor workers and the urban poor in particular. The IPCC assessments list increased heat-related mortality among the most certain health effects of warming.

Deaths from cold waves would tend to fall in a warmer climate, not rise. Floods and droughts (printed 'draughts') are expected to become more frequent and severe, and sea-level rise increases rather than decreases the risk of coastal flooding.

Answer: B

The gas that is not a greenhouse gas is argon (Ar).

A greenhouse gas absorbs and re-emits infrared radiation. Molecules with three or more atoms, or with an unequal charge distribution, can vibrate in ways that absorb infrared. Argon is a monatomic noble gas with no such vibrations, so although it is about 0.93% of the air, it traps no heat.

Ozone, carbon dioxide and methane are all greenhouse gases: carbon dioxide is the largest human contributor, methane is far more potent per molecule, and ozone in the troposphere also warms the surface.

Answer: A

The atmospheric window is the band of about 8 - 13 μm.

In this part of the thermal infrared, water vapour and carbon dioxide absorb only weakly, so much of the long-wave radiation emitted by the Earth's surface (which peaks near 10 μm) escapes directly to space. Only the ozone band at about 9.6 μm sits inside the window. Thermal remote sensing satellites use this band for the same reason.

The other bands are strongly absorbed: 5 - 7 μm lies in the water vapour band centred near 6.3 μm, and 14 - 17 μm lies in the strong carbon dioxide band centred near 15 μm. A band of 7 to 20 μm is far too wide and includes both of those absorption regions.

Answer: B

The albedo of the open ocean is minimum.

Water absorbs most of the sunlight that enters it, so a deep ocean surface reflects only about 6 to 10 per cent of incoming radiation when the sun is high. That makes it one of the darkest surfaces on Earth and a reason why loss of sea ice amplifies warming in the Arctic.

Snow and fresh ice have the maximum albedo, 0.8 or more. Bare soil reflects roughly 0.15 to 0.25, and wet soil, being darker, a little less than dry soil but still more than open water. So the ocean's albedo is lower than both soils, which rules out the options saying it is more than either.

Answer: B

The solar constant is 1345 W/M² in this paper's figure.

The solar constant is the solar energy received per unit time on a unit area held perpendicular to the sun's rays at the mean Earth-sun distance, outside the atmosphere. Because it is a flux, its unit is watts per square metre. Older textbooks quote values between about 1340 and 1370 W/m²; current satellite measurements put it near 1361 W/m², so 1345 is the textbook value the paper uses.

The options in W/M have the wrong unit for a flux. 1200 W/M² is too low, and 345 is closer to the average solar input over the whole globe (about a quarter of the solar constant), not the solar constant itself.

Answer: B

The answer is black carbon aerosols.

Black carbon (soot) absorbs sunlight strongly. The absorbed energy heats the layer of air in which the particles sit, while less sunlight reaches the ground, so the surface is dimmed and cooled. This combination of atmospheric heating and surface cooling is well documented for the South Asian brown cloud.

Ozone and the other greenhouse gases absorb outgoing infrared radiation and warm the surface as well as the lower atmosphere, so they do not cool the surface. Sulphate and nitrate aerosols mainly scatter sunlight back to space; they cool the surface but do not warm the atmosphere, since they absorb very little.

Answer: D

Among the options, the most abundant greenhouse gas is carbon dioxide.

Carbon dioxide is present at about 400 parts per million, far more than methane (about 1.9 ppm), nitrous oxide (about 0.33 ppm) or sulphur hexafluoride (a few parts per trillion). Strictly, water vapour is the most abundant greenhouse gas of all, but it is not among the options; the paper is asking about the well-mixed gases.

Methane and nitrous oxide are more potent per molecule than carbon dioxide, and SF₆ is the most potent of all, but potency is not abundance, which is why those options are wrong.

Answer: C

The increasing order is CH₄ < N₂O < SF₆.

Global warming potential compares the warming caused by a gas over a set period, usually 100 years, with that of the same mass of carbon dioxide. On the IPCC figures:

• methane: about 25 to 28
• nitrous oxide: about 265 to 298
• sulphur hexafluoride: about 23,000

SF₆ is the most potent greenhouse gas assessed by the IPCC, so any order that puts it first is wrong. The option ending in methane reverses the order of the other two as well.

Answer: B

The Montreal Protocol is about reducing ozone depleting substances.

Signed in 1987 under the Vienna Convention for the Protection of the Ozone Layer, it phases out the production and consumption of chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform and later HCFCs and methyl bromide. It is ratified by every country and is credited with the slow recovery of the ozone layer.

Greenhouse gas reduction and climate change are the subject of the UNFCCC, the Kyoto Protocol and the Paris Agreement. Hazardous waste is the subject of the Basel Convention. The 2016 Kigali Amendment added HFCs, which are greenhouse gases, but the Protocol's purpose remains the protection of the ozone layer.