Here’s an overview of what the IPCC report from Feb 2 contains. The full report for policymakers can be viewed here.
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New evidence indicates that humans are driving key components of global climate change.
- Global concentrations of CO2, methane, and nitrous oxide have increased markedly since 1750 due to human activity
- Human activity has led to global warming
- This warming is unequivocal
- Climate changes have also been observed at more detailed levels, affecting ice temperatures, ocean salinity, wind patterns, precipitation amounts, heavier precipitation, heat waves, and intensity of tropical cyclones.
- A few aspects of the climate have not been shown to have changed
- Paleoclimate information supports this period as unusually warm for the last 1300 years.
- Climate changes have been caused by anthropogenic greenhouse gas increases, at greater than 90% likelihood.
- Warming is projected at > 66% likelihood of being 0.2 degress C / decade; even if gases are held at 2000 levels, models predict 0.1 deg/decade
What is new about this report?
- This is the first report to provide a good estimate of “climiate sensitivity” – that is, the amount by which the atmosphere would warm if CO2 emissions were to double: 3 degrees C.
- This is the first report to demonstrate that human (anthropogenic) causes have driven atmospheric warming.
- More aspects of the climate have been measured with better accuracy than in previous reports.
What issues does this report raise?
- The IPCC takes a long time to present important research. Including consensus discussions amongst its 1,200 scientists. See this article from Nature for more info
- What will the next report be about? => I’ll get to this in a future post…
What is just cool about this report?
- Calculations of “Radiative forcing”. Radiative forcing is a measure of how much a factor influences whether there is a net influx (+) or outflux (-) of energy into the atmosphere. In other words, a factor that causes positive radiative forcing will warm the atmosphere. This report calculates that several human factors, greenhouse gases and ozone, lead to a net positive effect of humans on the warming of the atmosphere. Interestingly – several human factors, such as aerosols, create a negative forcing effect. (which is still drowned out by the positive factors).
- The attempt to simplify scientific jargon. Levels of statistical confidence are expressed in easy-to-understand terms such as “likely” and “virtually certain”. At first I thought this was silly, but now I see that it probably has more impact on a non-scientific audience than writing, P < 0.05.