aerosols and climate - a crash course marianne t. lund cicero nove mesto 17/9-15

Aerosols and climate- a crash course

Marianne T. Lund

CICERO

Nove Mesto 17/9-15

Observed changes in the climate system

IPCC 2013

We observe changes all across the climate system

"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millenia."

Global mean temperature

Global mean temperature anomaly

http://data.giss.nasa.gov

IPCC 2013

Increasing energy in the climate system more than 90% of

accumuated energy between 1970 and 2010 stored in the oceans

Global mean ocean heat content

Efficient heat uptake by the global oceans

Global mean ocean temperature anomaly

Warming also of the deep ocean (below 700 m)

Ice, snow and waterGlobal mean sea level change

Arctic summer sea ice extent

NH spring snow cover

IPCC 2013

Extreme events

Wuebbles et al. 2015

What drives the changes?

Perturbing the energy balance

Radiative forcing: changes in radiative balance

Natural and anthropogenic contributions

"(…) It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. "

IPCC 2013

A cocktail of emissions

Warming and cooling contributions

CO2, O3, N2O …

Oppvarmende Avkjølende

AEROSOLS

Radiative forcing 1750 to 2011

IPCC 2013

Aerosols

Definition

Main types of aerosols:• Dust• Sea salt• Sulfate • Soot (product of incomplete combutions)• Organic carbon• Products from biomass burning• Nitrate

“Aerosols are minute particles suspended in the atmosphere”

Natural and anthropogenic sources

Myhre et al. 2013

What do aerosols look like?

Heintzenberg et al. 2003

Aerosol sizes can vary from 1 nm to several 100 um

>10 um: giant aerosol

< 1 um: fine mode

Atmospheric life cycle

www.pnl.gov/

Aerosols have short atmospheric lifetime and are not well mixed like CO2.

Their impacts can be strongly localized, but aerosols can also be transported over large distances.

Aerosol distributions

Myhre et al. 2013

Aerosols are everywhere, but the amount and mixture of aerosols can be highly variable.

Aerosol impacts

Air quality and visibility

Health

Climate

Atmospheric circulation and precipitation

Diffuse radiation and photosynthesis

Air quality

Dehli Beijing

http://aqicn.org/map/

NY Times 14/2/2015

Aerosol health impacts

WHO: “7 million people died - one in eight of total global deaths – as a result of air pollution exposure in 2012.”

Aerosol climate impacts

Absorption and scattering of solar radiation

Warming Cooling

• sulfate• dust• Sea salt• Nitrates• Organic carbon

• Soot (black carbon)• Brown carbon (?)

More details from Bjørn…

Example: Volcanic sulfate

Mt. Pinatubo eruption

Example: soot on snow

Soot deposited on snow/ice absorbs radiation snow melt enhanced warming

AMAP 2011

Impact on clouds

More CCNs more, but smaller

droplets whiter cloud increased reflection

More CCNs more, but smaller

droplets longer cloud

lifetime

Local heating by soot Cloud burn-off

Low level clouds reflect solar radiation cooling

Myhre et al. 2013

Aerosol climate impact

Our models struggle to accurately represent aerosols and their impacts

measurements

IPCC 2013

How sensitive is the Earth’s climate to a doubling in CO2?

The stronger the aerosol effect until present, the higher the climate sensitivity

Reducing the uncertainties in aerosol climate forcing is crucial

Aerosols Greenhouse gases

1850 2015

+0.85o

Aerosols as part of the solution? Climate engineering

Summary

We observe changes all across the climate system consistent with a warming

It is extremely likely that human influence has been the dominant cause of the observed warming the last 60 years

Greenhouse gases (CO2) dominant warming impact, but important contributions from aerosols

Aerosols come in a number of types, shapes and sizes from numerous sources and have high spatial variability in the atmosphere

Aerosols influence climate through absorption and scattering of solar radiation and by making clouds whiter

Solving the challenges in aerosol science is a key priority

Reducing aerosols = co-benefits for air quality and human health