Detection, attribution, and future projections Flashcards
What policy makers (and the public) want to know
Has the climate really changed?
If it has, is the change due to human action?
Will there be significant change in the future?
To measure climate change, a baseline is needed
Meteorological records (vs previous normal period)
Once you start to change the climate it generates a set of effects in the earth system:
River gauge data (beginning of record?)
Glacial extent and mass balance (historical, photos, satellites)
Snow and ice extent (satellites- short baselines)
The biosphere (people, ecologists, satellites- few baselines)
Can the observed temperature change be simulated?
Play around with known forcing factors of temperature change to see if it looks like reality:
GHGs (positive)
Volcanoes (negative) (ash clouds dimming)
Solar variability (variable)
Anthropogenic aerosols (largely negative but highly uncertain)
Where could you get data on greenhouse gas concentrations come from?
Ice cores
Where could you get data on solar output?
Looking at cosmogenic isotopes such as beryllium which are affected by solar output
What is the aerosol thats most likely a positive forcing?
Black carbon/ soot landing on ice sheet and changing albedo
Simulated annual global mean surface temperatures
Natural - Sun and volcanoes - Omits anthropogenic Anthropogenic - Human - Omits natural All forcings - Red doesn't change in all observations - Key experiment : anthropogenic forcing becomes evident in past 30 yr - Not possible to replicate observations unless anthropogenic GHGs added
What is attribution?
Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth
Main points of attribution?
Total radiative forcing is positive- energy uptake by climate system.
Largest contribution is increase of CO2 since 1750.
Human influence detected in warming of atmosphere, ocean. Plus snow/ ice reduction and sea level rise.
Warming has become clear since about 1980- extremely likely human influence is dominant cause.
Can the observed temperature change be simulated?
Known forcing factors?
GHGs (positive forcing)
Volcanoes (negative forcing)
Solar variability (variable)
Anthropogenic aerosols (largely negative but variable)
What gives an indication of solar variability?
Volcanic eruptions
Historical
Ash in ice cores.