Modern Climate Change Darryn Waugh [email protected] OES Summer Course, July 2015.

Modern Climate Change

Darryn Waugh

[email protected]

OES Summer Course, July 2015

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

[email protected]

410-516-8344.