4.A - an effective response relies on knowing what the future holds

Question 1

what are some examples of positive feedback scenarios?

Answer 1

• global warming in the polar regions could be higher due to a reduced albedo effect
• clouds, particularly high clouds such as cirrus, can also trap outgoing heat and act as a blanket
• higher temps = more evaporation = therefore more water vapour which is a GHG…
• as temps increase in tropical regions, soil, plants and trees will become more heat stress, potentially releaseing the huge amounts of carbon they store
• rising sea temps could trigger the release of methane from methane hydrates stored on ocean floor

Question 2

what are some examples of negative feedback scenarios?

Answer 2

• rising global temps increase evaporation which increase cloud cover. clouds, particularly low clouds such as stratocumulus, reflect sunlight
• increased burning fossil fuels releases particulate into the atmosphere.
• absorption and reflection of insolation by these particles can reduce the amount of incoming energy.
• as temps increase, the areas in which trees can grow will extend north to higher latitudes. new trees will absorb more CO2

Question 3

how will past and present day GHG emissions affect the climate far into the future?

Answer 3

• many GHGs stay in the atmosphere for long periods of time
• as a result, even if emissions stopped increasing, atmospheric GHG concs would continue to increase and remain elevated for 100s of years.
• surface air temps would also continue to warm
• because oceans, which store heat, take many decades to fully respond.

Question 4

what are the 3 key global projections for temperature changes?

Answer 4

• increases in avg global temps are expected to be w/in the range of 0.5F to 8.6F by 2100
• global avg temp is expected to warm at least 2x as much in the next 100 years as it has during the last 100 yrs
• ground level air temps are expected to continue to warm more rapidly over land than oceans.

Question 5

what are the 4 key global projections for precipitation and storm events?

Answer 5

• global avg annual precipitation through the end of the century is expected to increase, although changes in the amount and intensity of precipitation will vary significantly by region
• the intensity of precipitaion events will likely increase on avg. particularly pronounced in tropical and high latitude regions
• strength of winds associated with tropical storms likely to increase.
• annual avg precipitation projected to increase in some areas and decrease in others

Question 6

what are the 3 key global projections for sea ice?

Answer 6

• for every 2F of warming, models project about a 15% decrease in the extent of annually avgd Arctic sea ice and a 25% decrease in the area covered by arctic sea ice at the end of summer. this decrease DOESN’T contribute to sea level rise
• coastal sections of greenland and antarctic ice sheets expected to continue to melt/slide into ocean. if the rate of this ice melting increases in the 21st c, ice sheets could add significantly to the global sea level rise
• glaciers are expected to continue to decrease in size = sea level rise.

Question 7

future sea level change projections?

Answer 7

• meltwater flowing from greenland ice sheet
• warming temps contribute to sea level rise by thermal expansion, melting mountain glaciers and ice caps and causing portions of the greenland and antartic ice sheets to melt or flow into the ocean
• since 1870, global sea level has risen by about 7.5 inches
• global sea level rise by another 1 to 4 feet by 2100

Question 8

future ocean acidification projections?

Answer 8

• ocean acidifcation adversely affects many marine species, including plankton, mollusks, shellfish and corals.
• if atmospheric CO2 concentrations double, coral calcification rates are projected to decline by more than 30%

Question 9

what does the most optimistic emissions pathway assume?

Answer 9

• assumes that CO2 emissions are at the peak now i.e. between 2010 and 2020.
• means that although the arctic may still warm by 2 degrees over the next 100 years compared to the 1985 avg.
• warming elsewhere will be confined to just 1-1.4C, with a 0.5C drop over the next 100-200 years from now
• precipitation is expected to increase by 10% in the mid latitudes over the next century

Question 10

what does the least optimistic emissions pathway assume?

Answer 10

• assumes that CO2 emissions will continue to rise w/in the next 100 yrs
• the arctic ocean will be completely ice free in September by the 2080s

Question 11

what are RCPs?

Answer 11

• the IPCC uses four scenarios called “Representative Concentration Pathways” (RCPs)

Question 12

how does an effective response rely on knowing what the future holds?

Answer 12

• we don’t know how severe future impacts will be because we don’t know what pathway we are on/what decisions future policy makers will make.
  (good AO2 point)

Question 13

what might a 2C world look like?

Answer 13

• raised sea level by thermal expansion alone 0.51-1.4m
• storm surges and increased hurricane destruction
• cities more likely to suffer from catastrophic flooding/super storms. impacts to infrastructure
• affect places we assume would be safe (not prepared)
• once in a century storms increase by 5x
• 35 mill Bangladeshi will become climate refugees
• superstorm sandy 2012 caused huge amounts of damage. could become more common

Question 14

what might a 3C world look like?

Answer 14

• possibility of releasing carbon locked in permafrost. 1500 billion tonnes of carbon (methane) 20x more powerful
• if it all melted from greenland = 7m sea level rise
• coastlines completely changing under this SL rise.

Question 15

what are the predicted impacts on global temperatures?

Answer 15

• many GHGs stay in the atmosphere for long periods of time.
• as a result even if emissions stopped rising, atmospheric gas concs would continue to rise and remain elevated for 100s of years
• moreover, if we stabilised concs, surface air temps would continue to warm
• this is because oceans store latent heat.
• except under the most aggressive mitigation scenarios, global temps are expected to warm at least twice as much as in the next 100 years as it has during the last 100 yrs
• ground level air temps are expected to continue to warm more rapidly over land than oceans. some parts of the world are projected to see larger temp rises than the global avg

Question 16

what are the predicted impacts on sea levels?

Answer 16

• warming temps contribute to sea level rise by expanding ocean water, melting mountain glaciers and ice caps and causing meltwater to flow from Greenland and antarctic ice sheets
• since 1870 global SL has risen by 7.5 inches
• estimates of future SL rise vary for different regions, but global SL for next century is expected to increase at a greater rate than during the past 50 years
• the contribution of thermal expansion, ice caps and small glaciers to SL rise is relatively well studied, but the impacts of climate change on ice sheets in Greenland and Antarctica are less understood and represent an active area of research.
• Changes in ice sheets are currently expected to account for 8 inches of SL rise by the end of this century

Question 17

what are representative concentration pathways?

Answer 17

• projections of what impacts climate change will have in the future under different emissions scenarios
• the IPCC uses 4 scenarios called RCPs.
• the numbers in the names represent radiative forcing = a measure of how the gases in the atmosphere affect the balance between the energy absorbed by the earth and the energy radiated back out to space.
• the bigger the number, the bigger the ratio of radiation in to radiation out.

Question 18

RCP 8.5 impact

Answer 18

• this emissions pathway assumes that CO2 emissions will continue to rise in the next 100 years.
• the Arctic Ocean will be completely ice free in Sept by the 2080s

Question 19

RCP 6.0 impact

Answer 19

• this emissions pathway issues that CO2 emissions will continue to rise until about 2100
• the arctic and antarctic will both see sig temp rises greater than 5C over the next 100yrs
• the Sahara will see a temp rise of 4C

Question 20

RCP 4.5 impact

Answer 20

• this emissions pathway assumes that CO2 emissions will continue to rise until about 2070
• the arctic will be particularly vulnerable over the next 100yrs with a 3-4C rise comp to the 1985 avg
• warming elsewhere will be confined to 2-3C
• arctic sea ice will also see considerable thinning

Question 21

RCP 2.6 impact

Answer 21

• assumes that CO2 emissions are at the peak now i.e. between 2010 and 2020.
• means that although the arctic may still warm by 2 degrees over the next 100 years compared to the 1985 avg.
• warming elsewhere will be confined to just 1-1.4C, with a 0.5C drop over the next 100-200 years from now
• precipitation is expected to increase by 10% in the mid latitudes over the next century