Unit 3 - CC: Evidence and Projections

Question 0

What is radiative forcing?

Answer 0

the change in average net radiation at the top of the troposphere (the lowest layer of the athmosphere) due to changes in concentrations of GHG or due to some other change in the climate system.

in other words the earth heat balance changes due to a change in radiation in or out. + radiative forcing is warmer athmosphere, - radiative forcing is colder athmosphere

Question 1

What are the main effects of rising temperatures on the climate system?

Answer 1

Rising sea levels
snow and ice melt
changes in weather patterns:
- frequency and amount of percipitation
- occurance and severity of extreme weather events

Question 2

The reasons of sea level rise?

Answer 2

1. thermal expansion of the oceans due to the fact that the ocean obsorbed more than 80% of the heat added to the climate system.
2. the discharge of additional water

(3. 2 mm/year between 1993 and 2010)
2. 0 / 1971 and 2010
1. 7 / 1901 and 2010

Question 3

Anthropogenic radiative forcings

Answer 3

1. increasing atmospheric concentration on greenhouse gases
2. opposite-sign effect of aerosols
3. emission of tropospheric ozone precursors (NO2, CO, hydrocrabons)
4. emissions of other greenhouse gases as halocarbons (incl. CFC’s)
5. Changes in the albedo

Question 4

The major scepticism around CC as a global issue

Answer 4

1. the existence and extent of past atmospheric temperature increase:
   - discrepancies between satellite and surface temp recordss
   - the effect of urbanisation on temperature records
2. the nature and severity of the impacts of atmospheric temp increase
3. the role of anthropogenic influences on atmospheric temp increases
4. the costs and benefits of measures for mitigation and adaptation

Question 5

What is committed warming?

Answer 5

The increase in global mean surface temperature that is inevitable - even if emissions are reduced - because of time lags in the response of various parts of the global climate system (especially ocean and cryosphere).

Question 6

What is the SRES?

Answer 6

IPCC Special Report Emissions Scenarios (2000)

4 narrative storylines
- A1 Rapid Convergent (economic) growth, with rapid introduction of new and more efficient scenario’s technologies (closes to BaU).
The 3 A1 groups show alternative directions of technological change in the energy system:
A1F1 Scenario - focus on fossil fuels
A1T Scenario - focus on other energy sources (non-fossil fuel)
A1B Scenario - a balance across energy sources
- A2 Unequal Growth / heterogeneous (diverse) world - with slower (economic) development, slow technology change and continuous increasing population (lack of economic growth in poorer regions)
-B1 Convergent more sustainable growth - shift to less material intensive and more sustainable systems.
- B2 - unequal but otherwise more sustainable growth.

Population
Economy
Technology
Energy
(Land Use)
Agriculture

5th assessment report introduced 4 new scenarios called Representative Concentration Pathways (RCPs).

Question 7

IPCC Climate Change Projections (8x)

Answer 7

1. temperature rise to 2100
2. Sea level rise to 2100
3. acidification of the ocean
4. changes in snow and ice
5. changes in precipitation
6. changes in extreme weather
7. changes in ocean currents
8. climate change beyond 2100

Question 8

what is the climate-carbon cycle coupling?

Answer 8

The interaction between climate change and a wide range of effects involving the carbon cycle.

The positive feedback mechanism by which carbon dioxide is released to the atmosphere as the climate system warms

Question 9

What are the possible feedback effects from loss of snow, ice and permafrost?

Answer 9

1. reduced albedo and greater surface warming from reduced surface ice and snow cover.
2. emissions of CO2 and MH4 from melting of the permafrost

Question 10

The Medidional Overturning Circulation

Answer 10

The MOC = transferring warmer waters to higher latitudes

Due to temp rise, and increased ocean temperature, the circulation will slow down. This can result in significant regional and local cooling effects, together with important ecological changes, on land and in the oceans, and with wider climate system effects.

Question 11

Average temp increase per decade?

Answer 11

0,2 degrees C per 10 yrs (until 2027)

Question 12

What has been the global mean surface temperature rise 1880-2012?

Answer 12

0.85+-0.2 (IPCC 2013) with significance in the last 50 years

Question 13

evidence for increase in global temp are?

Answer 13

1. satellite observations of air and sea temp increase
2. melting of snow and ice
3. increase in sea level

Question 14

the effect of increase ocean temperatures?

Answer 14

warm water holds less CO2 > positive feedback > CO2 is released > increased athmospheric CO2 > positive radiative forcing > greenhouse effect > further temp increase etc.

Also release of methane when warmer water in colder areas.

Question 15

temp increase leads to ecosystems moving away to colder areas (higher altitudes) challenges are:

Answer 15

1. ecosystems already on tops of mountains cannot go anywhere
2. the collapse might be quicker than the move (trees and soil take long time to move)
3. adaptation to other areas migh be hindered by other CC induced changes or by other pressures like pollution
4. loss of carbon sinks

Question 16

levels of CO2 in the athmosphere

Answer 16

280 ppm - pre industrial (before 1750)
380 in 2005
>400 in 2013

fossil fuels and land use

Question 17

State the main effects of rising global temperature

Answer 17

• increase in water vapour
• change in cloud coverage
• change in percipitation patters
• increase in average temp of ocean
• expansion of ocean
• ecological changes (due to ocean temp & due to temp)
• increased acidity
• ocean releasing CO2 or reduce absorbtion
• reduced snowfall, less ice coverage
• rising sea levels

Question 18

the main positive climate system feedbacks that (may) occur with rising global temperatures

Answer 18

• increased evaporation and increased water vapour in atmosphere (GHG) > increased clouds may be positive feedback
• snow/ice melt reduces albeido
• increase ocean temp = less CO2 in water (reduce uptake or release)
• reduce CO2 uptake or increase release in organic soils due to soil breakdown
• increase temp may cause forest die-back and fires
• melting permafrost (methane and CO2 release)
• higher winter temp reduces the biological pump which causes SO2 to be trapped by plankton falling to the ocean floor.

Question 19

Lifetime of CO2

Answer 19

there is a long timelag.

it will take between 50-200 years, although (Denman, 2007) says 30 years, for 50% of the CO2 to go away.

However a fraction (20%) stays behind for thousands of years

(Methane 12 years)

Question 20

CC Forecast and projections

Answer 20

CC forecast = short term
CC projections = long term

CC is complex, bit all forcing and feedback is understood fully, time lags, and it heavily depends on human behaviour!

Question 21

IPCC CC projections

Answer 21

IPCC 2013 projections by 2100

• temperature 2 degrees increase
• sea level rise 0.03 - 0.2m
• artic sea ice extend 43-94% less by end summer
• global glaciar volume 15-85% less
• Near-surface permafrost 37-81% less
• rainfall increase in high latitudes and decrease in subtropical terrestrial areas.
• Meridional overturning circulation (MOC) reduces with 25%