modern climate change darryn waugh [email protected] oes summer course, july 2015
TRANSCRIPT
IS THE EARTH’S TEMPERATURE CHANGING?
Focus on last 160 yrs
Climate over last 160 Years
Surface measurements show clear warming over last 100 yrs. Last decade warmest on record.
Annual average Temperature (relative to 1961-1990)
Climate over last 160 Years
Past Climate: Last 2000 years
Large uncertainty in temperature before 1850s, but all reconstructions show that global temperatures over last 30-40 years have not occurred in at least 2000 years.
Spatial Variations in Temperature Trends
Although global warming has occurred, this does not mean warming everywhere. More rapid warming over land than oceans.
[IPCC AR5]
WHAT ARE OTHER CHANGES IN THE CLIMATE SYSTEM?
Ocean Heat Content & Sea Level
[IPCC AR5]
Arctic Sea Ice
[IPCC AR5]
Land Surface Temp.
Sea Surface Temp.
Marine Air Temp.
Sea Level
Arctic Sea Ice
NH Snow Cover
Glacier Mass Balance
Specific Humidity
Ocean Heat Content
Tropo-spheric Temp.
Reading Material
Homework
[IPCC AR5]
Observed Changes in Climate System
Positive Proof
WHAT ARE THE CAUSES OF MODERN CLIMATE CHANGE?
What has caused for the observed warming over the last 160 yrs?
WHAT HAS CAUSED THE RECENT CHANGE IN EARTH’S TEMPERATURE?
The suspects:– Orbital variations– Volcanoes– Solar Irradiance– Internal variability– Greenhouse gases
The suspects:– Orbital variations– Volcanoes– Solar– Internal variability– Greenhouse gases
For last 50 yrsN time scale too long (>10,000 yrs)N no sustained forcing (2-3 yrs)N no trend since 1960s N inconsistent with last 2000 yr record
Y time scale correct + consistent with theory and measurements.
WHAT HAS CAUSED THIS CHANGE IN EARTH’S TEMPERATURE?
Surface Temperature and Solar Variations
No trend in solar irradiance in recent decades => Changes in solar irradiance can not explain increase in surface temperature over this period.
IPCC, 2007
Greenhouse Effect
Absorption by Gases
Atmospheric CO2: 1958 to present
Surface CO2 measurements show long-term increase + annual cycle
Mauna Loa
South Pole
Atmospheric CO2: 1000 to present
Greenhouse Gases (GHGs)
Concentrations of CO2, N2O, CH4 (“Greenhouse Gases”) have increased dramatically over last 150 yrs.
Temperature and CO2
20001000
1st Oil Well
Attribution
Need to also consider changes in aerosols, clouds and land surface (as well as solar, volcanic eruptions, etc.) for a quantitative understanding of cause of warming.
Increases in GHGs has been major contributor to warming.
WHAT MIGHT HAPPEN IN THE FUTURE?
To make projections of the future climate need
1. Numerical models to integrate together different components and processes, and
2. Projections of future emissions of greenhouse gases (and changes in land use), which depends on human behavior and activities.
Climate Models
Predicting Future Emissions
Future emissions of greenhouse gases (and changes in land use) will depend on several on different factors. E.g.
• Global Population trends
• World Economic Growth
• Source of Energy
• Technological Trends
• Policies
• Historical events (wars, political transitions).
All above are affected by human behavior and activities.
CO2 Emission Scenarios
A1B - balance between fossil and non-fossil fuels.
A1F1 - fossil fuel intensive.
A1T - large shift to non-fossil fuel.
B1 - sustainable development
A2 - heterogeneous would .
[IPCC 2001] Projections since 2001
Temperature Projections: 2005-2100
High Emissions
Low Emissions
Temperature Changes: Spatial variations
Warming is largest in NH high latitudes (ice feedback) and larger over land than oceans (heat capacity).
Minimum over North Atlantic Ocean and Southern Ocean
High EmissionsLow Emissions
Sea Level Rise
High Emissions
Low Emissions
Sea Ice Predictions
• All models predict continued retreat of Arctic sea ice. • Some predict complete ice free summers by end of the century.
Rainfall
Less rain in dry regions - DroughtsMore rain in wet regions - Floods.
High EmissionsLow Emissions
Heat Stress
“Global Climate Change Impacts in the US”
Report from US Global Change Research Program
http://www.globalchange.gov
Impacts separated by Regions and Sectors
Impacts of Climate Change
“What’s the worst that could happen?” [A rational response to climate change debate]
Greg Carven
http://www.youtube.com/watch?v=zORv8wwiadQ
http://manpollo.org/education/videos/how_it_all_ends/how_it_all_ends.html
Areas of Response
Geoengineering
• Mitigation - reduce the emissions of GHGs that cause climate change.• Geoengineering - manipulate the climate system to offset climate
effects of increased GHGs.• Adaptation - adjust human society to changing climate to reduce
resulting harms.
Stabilization Wedges
TAKE-HOME MESSAGES
Restatement of IPCC (2013) conclusions:
• We know that the climate is warming.
• We’re very sure humans are to blame.
• The future is hard to predict, but it’s certainly possible that
“business as usual” will lead to a catastrophic warming.
Contact: Darryn Waugh
410-516-8344.