GEO 011 Midterm 2 Study Guide

How much will sea level rise with an eventual melting of Greenland / West Antarctic ice sheet?

Greenland: 5-7m West Antarctic: 5m

What are some of the uncertainties associated with IPCC projections of future sea level rise

Newly observed phenomenon is accelerating ice sheet melting. Crevices in the ice sheets get filled with meltwater and lubricate the base, making it easier for large pieces of the ice sheet to fall into the ocean

Will sea level rise happen everywhere over the globe?

No due to rising coastlines in Eastern Canada after the rebound effect of recovering from the last ice age

Which continent will see the most warming?

North America has the potential to see the most warming

What causes the delay in warming in response to a doubling of CO2?

The ocean surface temperature's slower warming relative to land surface temperature warming

How is sea level projected to change by 2100? Why?

0.5-1.2m by 2100 because of water expansion as it gets hotter and continental ice sheets melting

What are the negative feedbacks associated with the carbon cycle?

1. Land Biosphere Feedback: More CO2 -> plants absorb more CO2 -> more plants 2. Ocean Carbon Cycle Feedback: Ocean acidification reduces production of CaCO3 by organisms -> less CO2 production in the ocean -> more atmospheric CO2 absorption 3. Rock weathering

What are positive feedbacks associated with the carbon cycle?

1. Land Biosphere Feedback: Warmer land -> increased growth and respiration of soil microorganisms -> carbon in soils becomes CO2 in atmosphere 2. Ocean Carbon Cycle Feedback: Warmer ocean has less ability to absorb CO2 in atmosphere 3. Biological Pump Feedback - less CaCO3 -> dead organisms do not sink into deep ocean -> weakens pump -> less CO2 can be absorbed by sea surface waters - Slowing of ocean circulation reduces the mixing of nutrients -> biological productivity slows and weakens biological pump

Accordingly to IPCC AR5, what is the range of climate sensitivity?

1.5 to 4.5 degrees Celsius

What the best estimate of climate sensitivity?

3.0 degree Celsius

Does all of our CO2 emission stay in the atmosphere? If not, where does it go?

55% of CO2 emissions do not go into the atmosphere. They go into the oceans or are absorbed by living biomass via photosynthesis

What is "climate sensitivity"?

Amount of change in the climate expected to occur with correlated changes in the factors that control climate

what other animal species will be at particular risk of extinction under continued climate change?

Amphibians, birds, and reptiles in cloud forest ecosystems. Trade winds rise up mountain slopes and condense at higher elevations so the clouds no longer intersect with forest floor, so forests are drier and nights are warmer. Also polar bears

What are the main reservoirs of carbon and processes of carbon transfer in the carbon cycle? Is photosynthesis important? Respiration?

Atmosphere, ocean, vegetation, soils, and detritus Photosynthesis and respiration are two of the few modes of carbon transfer between the biosphere and the atmosphere

How are floods and droughts projected to change? Why?

Because of decreased summer precipitation in the mid latitude regions, they will expect to see more droughts during the summer. Because of increased winter precipitation in polar and sub-polar regions, they will expect to see more floods during the winter.

How were atmospheric concentrations of greenhouse gases (GHGs) different during the LGM? Sea level? Ice sheets?

CO2 was at 180 ppm (half of what it is today), methane was about 1/5 what it is today, nitrous oxide about 1/3 what it is today. The global sea level was 120m lower. Ice sheets covered what is today Canada, northern USA, Scandinavia, and Europe and half of cooling during the LGM was due to ice sheet albedo

How does climate change affect ecosystems? Biodiversity?

Climate change is affecting the climate faster than ecosystems can adapt, pushing ecosystem resilience and may cause us to lose biodiversity

According to the IPCC, what is the most vulnerable ecosystem? Why?

Coral Reefs, they have little scope for adaptation caused by overfishing, pollutant runoff, fuel spills, fuel and wastewater discharge from boats, oil spills, and coral bleaching of algae that live on coral

List ecosystem boundaries delineated by climate.

Desert, subtropics, tropical rain forest, ecosystems near equator, tundras (near the poles)

How was the Last Glacial Maximum (LGM) different than today? Why is the LGM cooler than today?

During the Last Glacial Maximum, the earth's tilt was so that during the summer, the Northern Hemisphere received less direct sunlight, so it was cooler as more polar snow could accumulate into the summer.

How does the tropical Pacific change during El Nino? La Nina? How long will it alternate between El Nino and La Nina?

El Nino: Southeast trade winds weaken or reverse, warm water flows eastward accumulating at South American shores, cold water upwelling reduced due to weak winds. South America rains a lot. La Nina: Warm water accumulates around Australia, southeast trade wind far stronger than usual, upwelling of cold water, cold sea surface temperatures in eastern Pacific. They will alternate every few years

How is extreme weather projected to change? Severe frosts? Heat waves? Intense rainfall events and flooding? Dry spells? Hurricanes?

Extreme weather events will be even more intense, except for severe frosts, which will decrease in quantity and quality. Heat waves will be longer, more frequent, and more intense in western US, North Africa, and Middle East. Rain and snow events will be more extreme but will be separated by longer dry spells. We cannot determine whether there will be more or less storms and hurricanes, but they will be more intense with more downpour and flooding.

What is a hysteresis loop? Tipping points? How are they related to "abrupt climate change"? Be familiar with the case of ice sheets

In a hysteresis loop, there are two stable states. In terms of climate science, there is a stable point where ice growth overpowers ice melting and then a tipping point where ice melting overpowers ice growth. These are the two stable states. The tipping point is where it becomes extremely difficult to destabilize one state to another. The edge of the West Antarctic ice sheet has retreated into the sea. The rest of the glacial mass has less friction to reduce ice from land going into the ocean, so ice sheet melting has reached a tipping point toward accelerated melting.

What will be human loss in the coastal regions that are even not inundated by higher sea level?

Loss of life, property, infrastructure, degraded water quality, decreased availability of fresh water (salt water intrusion), loss of coastal habitats, significant population displacement

How are sunspots related to solar intensity? In modern climate, are there more sunspots (a brighter sun) than those (that) in the Little Ice Age?

More sunspots = warmer Fewer sunspots = less warm There are more sunspots in the modern age than during the Maunder Minimum and Dalton Minimum eras

What is El Nino Southern Oscillation (ENSO)?

Natural and irregular oscillations in the climate system involving inter-related changes in sea surface temperatures, currents, and winds across the tropical Pacific.

What is the "faux pause"? Can it be simulated by most model simulations? What caused it? Is it truly indicative of a pause in global warming?

Over the past decade, temperatures haven't been warming as much they did in prior decades. It was not simulated. It was probably caused by background volcanic activity, changes in solar output, and La Nina events in the Pacific. No it is not indicative of a pause in global warming, in fact, the increasing heat content of the ocean and the accelerated melting of Arctic sea ice have proven otherwise

How is precipitation projected to change? Why?

Poleward shifts in jet streams may cause increased winter precipitation in polar and sub-polar regions and decreased summer precipitation in the mid-latitude regions. Poleward expansion of the Hadley cell will cause decreased precipitation in the subtropics. Increased temperatures will cause more precipitation near the equator

What do fossil-fuel emissions scenarios consider?

Population growth and per capita energy consumption, which are both closely linked to economic growth and technological advances that can accelerate consumption and shift it to climate neutral alternatives to carbon

Why coral reefs and wetlands are important?

Provide food, defense against tropical cyclones, and are a billion-dollar tourism spot

Why are ecosystems valuable?

Provide resources, regulate the environment, and for recreational reasons

Under climate change, what are the threats to coastal and low-lying regions (e.g., Bangladesh, Southern Florida, Netherlands)?

Rising sea level, increased cyclone intensity, increased coastal erosion, and larger wave heights

Where do estimates of climate sensitivity come from?

Take climate models and try to match their predictions with the observed changes in climate by tuning climate sensitivity

Is the surface warming spatially uniform? What are the warming patterns and reasons?

The surface warming will not be spatially uniform. The polar regions will warm the most due to positive feedback loop of melting ice. Land will warm faster than the oceans as water absorbs heat slower than land. North Atlantic warming will be weak due to changes in ocean currents (weakening of Thermohaline Circulation).

What are the characteristics of ENSO projections (climate overall? ENSO magnitude?) Are ENSO projections certain?

There are no certain projections due to how unpredictable ocean current changes are, especially during ENSO

How are Representative Concentration Pathways (RCPs) defined? What is meant by a "business-as-usual" scenario? A conservation/mitigation scenario? What is RCP8.5? RCP2.6?

They are defined by radiative forcing. Business-as-usual means increased carbon consumption over the next century. A conservation/mitigation scenario is one where we conserve carbon consumption and reduce it while also mitigating the effects of climate change with good policies. RCP8.5 represents the business-as-usual scenario while RCP2.6 represents the conservation/mitigation scenario.

How well did past IPCC projections do? Does IPCC overstate the effects of climate change?

They were very accurate. Sea level rise projections have fallen with each IPCC report, but projections are consistent with observed acceleration. Melting of ice sheets has begun earlier than projected and the upper end of the AR5 projections have been shifted to compensate. Arctic sea ice have been melting faster than projected

Under RCP8.5, how much warming does IPCC project by 2100? Under RCP2.6? Note the warming magnitude relative to 2000 and relative to preindustrial.

Under RCP8.5, about 3-5.5 degrees Celsius. Under RCP2.6, between a little over 0 degrees to under 2 degrees Celsius. Relative to 2000, about 0.2-1.8 degrees Celsius. Relative to pre-industrial times, about 2.5-4.6 degrees Celsius.

Why are future projections of climate change uncertain? Or more specifically, what are the two main sources of uncertainty? What is meant by climate change "uncertainty"?

Unknown trajectory of future GHG emissions and unknown climate response to these emissions

How does global warming affect air pollution? Why?

Warmer temperatures -> more tropospheric ozone pollution and air stagnation

What are required to achieve lower stabilization targets? To stabilize CO2 level at 450, 550, 750 ppm, by which year we need to reach emission peak?

We need sooner peak CO2 emissions followed by a sharp reduction of emissions afterwards. 450 ppm: 2020 550 ppm: 2040 750 ppm: 2080

How has CO2 varied over geologic time scales? Has it varied a lot, or a little?

there was a carbon maximum 500 MYA which fell 300 MYA at the height of the Permo-Carboniferous glaciations on Gondwana. Then there was another maximum 175 MYA in the late Triassic period

With 6 meters of sea level rise, will most of New York City be submerged?

yes.