space weather impact on climate? -...

efc &-1 /July 2002Alpbach Summer School 2002 on Space Weather: Physics, Impacts and Predictions

Space Weather Impact on Climate?

Alpbach Summer School on Space Weather: Physics,

Impacts and Predictions

Eigil Friis-Christensen


Solar Activity and Monsoon Precipitation in Oman

Stalagmites in caves in Oman show that changes in monsoon precipitation during 3000 years is strongly correlated with changes in solar activity.

Past northwardshifts of the intertropicalconvergence zone

U. Neff et al., Nature 411, 290-293, 2001


What Are the Causes of Climate Variations?

Internal oscillations in atmosphere-ocean systemVariation in energy received from the Sun: • Solar irradiance variations - various spectral bands.• Cloudiness.• Volcanic dust and aerosols.• Other aerosols, natural and human induced.

Variation in energy radiated away from Earth: • Atmospheric properties, in particular greenhouse gasses like

– CO2, Methane, CFCs, Ozone.– Cloudiness and water vapor (important part of feed-back mechanisms).

• Surface properties like– Ice cover, land and ocean.– Vegetation.– Land erosion.


How Do We Define Solar Variability in This Context?

Total solar irradiance• Relatively small during a solar cycle (0.1%)• Long-term variations (0.25%?)

UV-radiation changes• Small power compared to the visible part of the spectrum.• Relatively large variation during a solar cycle (> 1% at

stratospheric heights, even more at higher altitudes)

Changes in the solar wind (heliosphere)• Extremely small power.• Very large relative variations during a solar cycles - and on

longer terms.• Earth’s surface modulation of cosmic ray flux ~ 20%• Middle atmosphere formation of odd Nitrogen


Irradiance measurements are made by several instruments on SOHO:

VIRGO - Total solar irradianceSEM (Celias): EUV disk integrated flux from 1-770Å and in He II 304 ÅCDS: EUV 307-380 Å and 515-632 Å Spectral irradiance and 69 full disk images taken each month


Sunspots – an “indicator” of Solar Energy Output


Magnetic fields on the Solar surface


Sunspot Number R

1750 1800 1850 1900 1950 2000Year

50

100

150

200

250

300

R

Sunspot number R, monthly values

Period between 9 and 13 y

Longer periods exist, 60-100 y


Earth’s Magnetic Field and the Heliosphere

Earth’s magnetic field and production rate of Carbon-14 caused by cosmic rays

Solar wind variations affect the production rate of C-14


Production rate C-14 and Be-10


Maunder Minimum

Reconstructions of Solar irradiation indicate very small variations at a very low level

Beryllium-10 isotope indicate a significant modulation caused by changes in the cosmic ray flux – likely caused by changes in solar magnetic fields.

Reconstructed temperatures follow Be-10


Solar Variability Seen in the Atmosphere


Solar and Geomagnetic Activity

Yearly average Geomagnetic activity index (aa)Sunspot number (R)

Solar activity ~ 11-y period. The rhythm, not the form, is reproduced in geomagnetic activity. Long-term variation is differentConclusion: R and aa are different manifestations of solar energy output


Global temperature and sunspots


Global Temperature and Cycle Length: An Update

During the latest about 20 years, temperature has increased more than expected - based on the length of the solar cycle

The effect of enhanced greenhouse effect is finally seen

The climatic effect of solar activity is not fully described by the length of the solar cycle

Surface temperature are not representative (Satellite MSU measurements)

IPCC 1990: Increase by 0.3 to 0.6°C over last century broadly consistent with climate model predictions.FCL 1991: Major part of temperature changes during last century well correlated with solar activity.IPCC 2001: Temperature increase during the last 50 years mainly caused by human activity.


Sun-climate relationship – in a longer perspective

Correlation between SCL og GR-LA temperature for 1590-1970 gives thefollowing Correlation Coefficient:

Temp. ref. 1881-1975:

-0.79

Temp. ref. 1950-81:

-0.83

Groveman og Landsberg (GR-LA) 1979 reconstruction


Spring in Middle and Lower Yangtze River Valley

Phenological data -personal diaries and other documents• Time of blossoming of

specific plants• Last day of snow events

Spring time - “days before and after an average date” • (Hamed and Gong,

1993).• 10 years average

Solar cycle length, L

1600 1700 1800 1900 2000Year

-15

-10

-5

0

5

10

15

20

Day

s

8

9

10

11

12

13

14

Years

dageL

9 10 11 12 13Cycle Length (years)

-15

-10

-5

0

5

10

15

20

Day

s


Temperature variations during 1000 years

11-year mean values,Jones et al. (1998)

and

Reconstruction of thetemperature at Dye-3 based on directtemperature measurements in bore hole


Past Temperature

Jones et al.No assumptions

Traditional averaging

Mann et al. Assumptions:

Relationships between temperature variations at different sites are unchanged in time

11-Year Mean Values of Reconstructed Temperatures


Past Temperatures - Greenland Ice Sheet

Reconstruction of past temperatures based on bore hole data from two sites:

Dye-3 and Gripon the Greenland Ice Sheet.

Dahl-Jensen et al.Science 1998


Reconstruction of temperature


Temperature observations –at surface and measured with balloon


Cosmic Rays and Clouds


Atmospheric Ionisation Density Profile

Viggiano and Arnold, 1995


Ion pair production over Thule

SolarMinimum

SolarMaximum

“The meteorological variable subject to the largest solar-cycle modulation in the dense layers of the atmosphere is the atmospheric ionisation produced by cosmic rays.”

E.P. Ney, Nature, 1959.


Cloud Types and Cosmic Rays

High (< 440 hPa)

Middle (440-680 hPa)

Low (>680 hPa)

Cosmic Ray Intensity -Huancayo


Long term drifts in cloud data

ISCCP Low IR (blue)SSMI (green)

Average based on areas of high correlation

Average land and oceansblue: ISCCP Low IRgreen: adjusted according to linear trend from above


Radiation Properties of Clouds

High Clouds MiddleClouds

LowClouds

Thin Thick Thin Thick AllTotal

GlobalFraction % 10.1 8.6 10.7 7.3 26.6 63.3Net CloudForcingWm-2

2.4 -7.0 1.1 -7.5 -16.7 -27.7


Possible Causes of Cloud Variability

Volcano's

El-Nino

Clouds and Cosmic Rays


Low cloud cover – cosmic rays – and ENSO


Low cloud top temperature – cosmic rays – and ENSO


Aerosols and Cloud MicrophysicsSatellite Observations of Ship Tracks

Visible: 0.9 µm NIR-IR: 3.9 - 10.7 µm


Formation of Ultra Fine Aerosols ( ~ 3 nm)

Homogeneous Nucleation

Ion Mediated Nucleation

Nuc

leat

ion

rate

(P

artic

les p

r se

c pr

cc)

Hom

ogen

eous

Ion Mediated Nucleation

H2SO4 molecules pr cc

1

+

+

_

_107 108

0.1

10

100

0.01

Range based on observation over the Pacific Ocean (Clarke et al. 1998)


Physical mechanisms - formation of clouds

Low clouds are affected• Implies an effect on water vapour clouds - not ice clouds• Aerosols - via production of cloud condensation nuclei (CCN) - are

important for the cloud formation • How are CCNs formed?

– Insufficient understanding• Do electric charges play a role?

– Yes, according to new research results, computer simulations• What is missing?

– Experimental proof


Physical processes and their implementation in climate models

Changes in total irradiance• Easy to include in models, but effect is small.

Changes in UV-radiation• Modulation of ozone concentrations modify vertical transport• Decadal variations in observed parameters can be modeled.• Significant regional effects on surface temperature - small global effects

Changes in energetic particle flux• Cosmic ray flux

– Direct change in cloud nucleation processes.– Via changes in atmospheric electricity and electro freezing.

• Energetic electron precipitation– formation of middle atmosphere Noy - transport to stratosphere– contribute to the destruction of Ozone


Conclusion

Changes in total irradiance• Some effect is probable

Changes in UV-radiation• Decadal variations in observed parameters can be modeled• Systematic effects observed at high altitudes - less at the surface

Changes in energetic particle flux• Cosmic ray flux

– Effect on cloud nucleation seems a promising mechanism - potentially large effect

• Energetic electron precipitation– effect on ozone may be similarly effective as UV effect

All components may work together– and do not exclude an effect of the increased amount of greenhouse gases

space weather impact on climate? -...

Documents