climate suprises

Question 1

Thresholds and tipping points

Answer 1

• A point where there is a change in the system that can be reversed
• The climate system can switch into a new state very quickly once a threshold has been passed
• A threshold can become a tipping point that, when crossed means the system moves into a new state, this is irreversible

Question 2

examples of tipping points

Answer 2

• ENSO changes
• Permafrost loss
• Runaway positive feedback loop of Ch4 release triggered by increase in temperature
• Boreal forest dieback
• Arctic sea ice loss
• Greenland ice sheet melting, could increase sea level rise by 7m and disrupt Atlantic deepwater formation
• Amazon rainforest dieback, hypernino from climate change would result in long dry spells in Amazon
• Instability of West Antarctic Ice Sheet, could increase sea level rise by 8.5m and disrupt AABW formation
• Sahara greening
• West African monsoon shift
• SE Asian monsoon instability

Question 3

linear but delayed response of system to climate forcing

Answer 3

• Magnitude is proportional to the additional forcing
• Initial delay
  E.g. heating of the oceans, takes a lot of energy to increase temperature at first due to inertia but then steadily rises

Question 4

Muted or limited response of system to climate forcing

Answer 4

• Effect is not directly linked to additional forcing
• Relevant part of climate system is buffered in some way
  E..g East Antarctic ice sheet has remained stable in much warmer periods of geological history (on land, so more stable)

Question 5

Delayed and non-linear response of system to climate forcing

Answer 5

• Climate system may have an initial slow response, but then responds in a non-linear way
• Related to positive feedback mechanisms e.g. albedo lost as ice sheets melt

Question 6

Threshold response of system to climate forcing

Answer 6

• Very little response until it reaches a threshold
• The response then takes place over a very short period of time
  E.g. if the Greenland ice sheet starts to melt, the melting could start to accelerate causing a catastrophic collapse