Climate Models Flashcards
What are the 3 types of climate model?
- Energy Balance Models
- Global Climate Models/General Circulation Models (GCMs)
- Earth System Models of Intermediate Complexity (EMICs)
Definition of climate model
Numerical representation of the climate system with differential equations representing processes in atmosphere and oceans
What are the pros and cons of energy balance models?
- Simple, quick to run, easy to understand
- leaves out many processes
What is an energy balance model?
Looks at shortwave solar radiation coming in and long wave emitted from earth
Simple box models for ocean, carbon cycle etc
Generally used for studies of sensitivity of Earth system to major radiational changes
Example of energy balance model
Monash simple model
aids conceptual understanding of the climate response to forcings, and as a tool for education
Has all the forcings and can alter these.
Observed data used for ocean and climate
No thermohaline or atmospheric circulation
Very coarse resolution
Pros and cons of EMICS
- good for incorporating lots of doffing components
- good for long term simulations, even glacial cycles
- quite coarse resolution
- most processes are in parameterised form
Example of EMIC
Love clim
Has atmospheric circulation, thermohaline circulation, ice sheet flow, vegetation dynamics, terrestrial and oceanic carbon model
What is the project that the IPCC does for past modelling comparison?
Palaeoclimate Modelling Intercomparison Project (PMIP)
Understand the mechanisms of climate change
•Identify the different climatic factors that shape our environment
•Evaluate the capability of state-of-the-art models to reproduce different climates
Different time periods worked on:
- mid- Holocene
What happened in the mid- Holocene project?
Green Sahara:
Procession had changed, with the perihelion being different
More solar radiation in summer in the northern hemisphere
larger temperature and air pressure gradient and stronger winds coming from ocean
Stronger monsoons
Proxy data from lake sediment cores show 10x increase in precipitation compared to present day, with the Sahara being vegetated with herbaceous and woody vegetation. Precipitation was the most important but temperature, changed fire dynamics, and soil texture was also important in determining vegetation composition.
Model validated proxy data and showed the processes
How much warmer is it now that between 1850 and 1900?
Global mean surface temperatures 2001-2020 were 1°c higher than 1850-1900 (IPCC 2021)
What is the definition of calibration?
Calibrating is obtaining a statistical estimate of the scaling factor relating a change in the proxy value (ring width etc.) to a change in temperature
Example for geographical extent and rate of warming
Reconstructed temperatures for each century (between 9th and 20th). Compared to reference period of 11th-19th century.
First widespread warming in 20th century
Temperature differences between centuries.
Highest rate of change between centuries is 1800s-1900s
Fernández-Donada et al., 2013
Proxy reconstructions of temperature from different continents, using different reconstructions and methodologies.
Timing of warm and cold periods is largely the same. With different magnitudes of change based on sensitivity of different proxies.
Southern hemisphere has less data available
Example for warming/rate of warming
Pages 2k.
International effort. Almost 700 proxy data sources including tree rings, Sediment cores, corals.
Unprecedented warming in the past 50 years. When compared to proxy data over last 2000.
Also found by IPCC.
Osborn and Briffa 2006
Took 14 proxy records that were:
- significantly positively correlated with local observed temperatures
- were accurately dated
- with data from 9th century to 20th
Smoothed to remove short term fluctuations
First widespread extended period of warming is in 20th century, over 100 years.
Indisputable evidence of warming
