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