L18

Question 1

What are the 3 methods to estimate future climate?

Answer 1

1 emission scenarios of all GHGs for the 21st century
2. 1% yr-1 CO2 increase (simple “what if?” scenario) for easier model inter-comparison
3 CO2 stabilisation (a “what would it require?” scenario)

Question 2

what are emission scenarios

Answer 2

• scenarios are alternative images of how the future might unfold and are designed to represent the range of driving forces
• highly unlikely that reality will follow a scenario exactly and they arent assigned probabilities
• they do not represent policy recommendations

Question 3

what are the IPCC AR4 storylines

Answer 3

designed to represent some scenarios with different levels of intervention

Question 4

describe storyline: A1

Answer 4

very rapid ecomonmic growth
lots of new technologies
population growth to mid 21st century

Question 5

describe storyline: A2

Answer 5

Continuously increasing population

Fragmented and slower economic growth and technological advancement

Question 6

describe storyline: B1

Answer 6

Same population as A1
Introduction of clean and efficient technologies
global solutions to environmental sustainability

Question 7

describe storyline: B2

Answer 7

Population similar to A2

local solutions to sustainability

Question 8

What are A1F1, A1T,A1B examples of

Answer 8

technological paths

Question 9

how do we stop co2 levels rising

Answer 9

stop anthropogenic emissions like 0 no messing about here

Question 10

how much warming predicted by 2100

Answer 10

2-3.5 but much larger locally

Question 11

how much do optimistic scenarios estimate co2 will rise by

Answer 11

2x

Question 12

There are four steps involved in projecting the future climate, three of them involving a climate model. What are these four steps?

Answer 12

The four steps are: 1) defining the emissions, 2) using a climate model to quantify the future changes in greenhouse gas and aerosol concentrations, 3) calculating the radiative forcing, 4) quantifying the response of the climate system.

Question 13

2. The SRES A2 and B1 scenarios are often cited as representative of the worst case and most optimistic case of future emissions. What is the global mean radiative forcing in 2100 in these two scenarios? What is the projected increase in temperature relative to the 1980-1999 mean?

Answer 13

2. The SRES A2 and B1 scenarios result in a global mean radiative forcing in 2100 of about 8 and 4 W m-2. The projected increase in temperature relative to the 1980-1999 mean is about 4 K and 2 K.

Question 14

3. Where are future temperature changes predicted to be greatest?

Answer 14

3. Temperature changes are projected to be greatest at high latitudes (mainly the Arctic) and at high altitudes (the upper troposphere).

Question 15

4. Describe roughly the global pattern of projected changes in precipitation.

Answer 15

4. Decreases in precipitation over most sub-tropical latitudes and lower mid-latitudes (southern Europe to north Africa) and increases at higher latitudes and in the tropics.

Question 16

5. If CO2 emissions were reduced below year 2000 levels by 10%, 30%, 50% or 100%, which one of these scenarios would lead to falling CO2 concentrations in the atmosphere?

Answer 16

5. The only scenario of CO2 emissions that leads to falling CO2 concentrations in the atmosphere is to cut the emissions to zero.

Question 17

6. What is a “CO2 stabilisation scenario”?

Answer 17

6. A “CO2 stabilisation scenario” is an estimate of how CO2 emissions would need to change in future in order for CO2 concentrations in the atmosphere to stabilise (i.e., remain constant) after some future date.

Question 18

7. If we wanted to stabilise CO2 concentrations at 450 ppm, describe roughly how the CO2 emissions would need to change in future.

Answer 18

7. If we wanted to stabilise CO2 concentrations at 450 ppm, the emissions would have to drop sharply to about zero by 2050. The emissions would then have to remain well below 1900 levels in order for 450 ppm to be maintained into the future.