SRON_Spectrum_2016

Photo: NASA.
In our atmosphere minuscule dust and
fluid particles that influence our climate
are floating around. Examples are sea salt
or soot particles from traffic. Yet how
these aerosols contribute to global
warming is still a mystery. Where exactly
are aerosols emitted? Are they harmful
for us? NASA’s climate satellite PACE
will search for answers to these and
other questions, possibly with the help
of a Dutch instrument.
Aerosols: missing link in climate research
15
SRON Spectrum
Global warming is one of the biggest challenges of this age. Models,
however, differ considerably with respect to the speed and extent to
which the climate is warming up. One of the reasons for this uncertainty
is that we still do not know enough about the mechanisms
under lying climate change. The influence of aerosols is one of the most
important climate factors that we still know relatively little about.
Aerosols are minuscule solid or liquid particles that float around in the
atmosphere. They can come from natural sources, such as ash from
volcanic eruptions, sand from the Sahara or sea salt from the oceans.
However humans also emit large quantities of aerosols with the combustion
of fossil fuels and wood. Dependent on their composition,
the particles can exert either a warming up or cooling down effect on
the climate. They influence the temperature through radiation effects
and cloud formation. Some types of particles cool the climate by acting
as tiny mirrors that reflect sunlight directly into space. Other types, how -
ever, can absorb solar radiation or heat emitted by the earth and then
emit this again as result of which the greenhouse effect is en hanced
and the atmosphere warms up. Aerosols also play a role in the formation
of clouds because water condenses on small aerosol particles and
consequently forms clouds. In turn these clouds exert an influence on
the climate system.
There are many different types of aerosol particles and their interactions
with the climate are complex. So at present we do not know how
aerosols contribute to changes in our climate. We are not even entirely
sure whether on balance aerosols enhance or mitigate global warming.
With our current level of knowledge, the uncertainty regarding the
worldwide effect of aerosols is just as big a factor as the total effect of
the greenhouse gas carbon dioxide. SRON program leader Avri Selig:
“To find out how aerosols influence the climate we must know exactly
how many particles are
“We are not even entirely
located where in the atmo -
sure whether on balance
sphere, whether these
aerosols enhance or mitigate
particles absorb or reflect
global warming...“
radiation, and what the
composition of these particles is. Furthermore, if we know the composition
of the particles we can determine whether they are harmful for
public health and how harmful they are. So far this knowledge is not
available on a large scale.”
The role of satellites
Measurements of aerosol properties on a global scale are needed to
understand the influence of aerosols on the climate and air quality.
Such measurements can only be obtained with the help of satellites.