Atmospheric Composition and Climate

E. MészárosUniversity of Pannonia

H-8201 Veszprém, P.O.B. 158.meszaroserno@invitel.hu

Atmospheric cycle of different constituents

• The Earth’s atmosphere consists of gas molecules (size: 10-10 m) and aerosol particles (1-10 nm-10 m).

• Atmospheric constituents are exchanged continuously in the air: there are sources (mostly biogenic) releasing them into the air, and there are sinks removing them from the air.

• Each molecule (particle) spend a certain time in the air: residence time. Examples: oxygen: 3000 years, carbon dioxide: 5 years, water: 10 days.

Biogeochemical cycle

The Earth’s atmosphere is a very significant environmental medium

• Protection against external effects: meteors, UV radiation, cosmic radiation, etc.

• Atmospheric constituents supply nutrients for the biosphere: water, carbon dioxide, oxygen, nitrogen and nitrogen compounds, sulfur species, etc.

• Atmospheric gases and aerosol particles control the solar and terrestrial radiation transfer, consequently the climate of the planet (the role of clouds).

Interaction with the biosphere

• The majority of atmospheric gases and particles is produced by biospheric emissions: the present air is the consequence of life on our planet. Living organisms control the atmospheric composition (example: microbiological processes determine nitrous oxide emissions which controls the ozone layer).

• Air constituents make the life on the planet possible (examples: photosynthesis, decomposition, respiration).

Atmospheric effects on terrestrial and aquatic ecosystems

• The different constituents leave the air by wet and dry deposition (sink processes). Wet deposition (materials removed by precipitation fall) is important in particular, providing for ecosystems (including agricultural lands) nitrogen (nitrate, ammonium ions) and sulfur (sulfate ions) containing compounds in dissolved form.

Human effects on depositions

• The emissions of sulfur (by energy production) and nitrogen oxides increase the hydrogen ion concentration leading to acid rains.

• The emissions of nitrogen compounds in oxidized or reduced (ammonia: agriculture) forms can contribute to eutrofication (excess nutrients (e.g. in shallow lakes).

Climate depends on radiation balance

Human activities and climate

• Emissions of certain gases and aerosol particles into the air modify solar and terrestrial radiation transfer: climate changes.

• Examples: 1. emissions of greenhouse gases like carbon dioxide

(fossil fuel burning), and methane (rice production, animal husbandry) can cause global warming owing to their long residence time.

2. emissions of aerosol particles and aerosol forming gases (short residence time) can cause cooling due to the direct and indirect (through cloud formation) extinction of solar radiation.

Present views about aqnthropogenic climate change (IPCC, 2008)

• The increase of the concentration of greenhouse gases in the atmosphere is certainly caused by human activities.

Continuation

• The temperature increase observed during the last hundred years (less than 1oC) is very probably man-made.

J. Lovelock (1988: The Ages of Gaia)

• „The atmosphere is the face of the planet, and it tells, just as do our face, its state of health and even if it is alive or dead.”

• Conclusion: Human race has to operate in such a way that our special atmosphere, essential for our own life, remain alive, that is compatible with our activities.

Thank you for your attention!