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Ulrich Elkmann Offline




Beiträge: 7.340

26.12.2017 02:46
Noch ein Weihnachtsgeschenk. Henrik Svensmark, Nir Shaviv antworten

Nach dem eindrucksvollen Himmelszeichen, das Elon Musk am Tag vor Heiligabend an den Himmel Südkaliforniens (wie passend) geschrieben hat mit der Start der 4. Tranche der Iridium Next-Satelliten, gewissermaßen eine Umkehrung des alten Klassikers "NORAD tracks Santa" - ein weiteres unerwartetes Geschenk, und es hat ebenfalls mit kosmischen Bereichen zu tun. Aus Nir Shavivs Blog:

Zitat
shaviv's blog /

Finally! The missing link between exploding stars, clouds and climate on Earth
19 Dec 2017

By shaviv

Blog topic:
astronomy, cosmic rays, global warming, personal research, weather & climate

By Henrik Svensmark and Nir shaviv

Our new results published today in nature communications provide the last piece of a long studied puzzle. We finally found the actual physical mechanism linking between atmospheric ionization and the formation of cloud condensation nuclei. Thus, we now understand the complete physical picture linking solar activity and our galactic environment (which govern the flux of cosmic rays ionizing the atmosphere) to climate here on Earth though changes in the cloud characteristics. In short, as small aerosols grow to become cloud condensation nuclei, they grow faster under higher background ionization rates. Consequently, they have a higher chance of surviving the growth without being eaten by larger aerosols. This effect was calculated theoretically and measured in a specially designed experiment conducted at the Danish Space Research Institute at the Danish Technical University, together with our colleagues Martin Andreas Bødker Enghoff and Jacob Svensmark.

Background:

It has long been known that solar variations appear to have a large effect on climate. This was already suggested by William Herschel over 200 years ago. Over the past several decades, more empirical evidence have unequivocally demonstrated the existence of such a link, as exemplified in the examples in the box below.

The fact that the ocean sea level changes with solar activity (see Box 1 above) clearly demonstrates that there is a link between solar activity climate, but it can be used to quantify the solar climate link and show that it is very large. In fact, this “calorimetric” measurement of the solar radiative forcing is about 1 to 1.5 W/m2 over the solar cycle, compared with the 0.1-0.2 W/m2 change expected from just changes in the solar irradiance. This means that a mechanism amplifying solar activity should be operating—the sun has a much larger effect on climate than can be naively expected from just changes in the solar output.

Over the years, a couple of mechanisms were suggested to explain the large solar climate link. However, one particular mechanism has accumulated a significant amount of evidence in its support. The mechanism is that of solar wind modulation of the cosmic rays, which govern the amount of atmospheric ionization, and which in turn affect the formation of cloud condensation nuclei and therefore how much light do the clouds reflect back to space, as we now explain.

Cosmic Rays are high energy particles originating from supernova remnants. These particles diffuse through the Milky Way. When they reach the solar system they can diffuse into the inner parts (where Earth is) but lose some energy along the way as they interact with the solar wind. Here on Earth they are responsible for most of the ionization in the Troposphere (the lower 10-20 km of the atmosphere where most of the “weather” takes place). We now know that this ionization plays a role in the formation of cloud condensation nuclei (CCNs). The latter are small (typically 50nm or larger) aerosols upon which water vapor can condense when saturation (i.e., 100% humidity) is reached in the atmosphere. Since the properties of clouds, such as their lifetime and reflectivity, depends on the number of CCNs, changing the CCNs formation rate will impact Earth’s energy balance.

The full link is therefore as follows: A more active sun implies a lower CR flux reaching Earth and with it, lower ionization. This in turn implies that fewer cloud condensation nuclei are produced such that the clouds that later form live shorter lives and are less white, thereby allowing more solar radiation to pass through and warm our planet.

Until today we had just empirical results which demonstrate that this link is indeed taking place. The main results are summarized in Box 2 below. In particular, we have seen correlations between solar activity and cloud cover variations, as well as between cosmic ray flux variations arising from changes in our galactic environment and long term climate change using geological data.



http://sciencebits.com/CosmicRays_Climate_TheMissingLink



"Les hommes seront toujours fous; et ceux qui croient les guérir sont les plus fous de la bande." - Voltaire

Ulrich Elkmann Offline




Beiträge: 7.340

26.12.2017 03:03
#2 RE: Noch ein Weihnachtsgeschenk. Henrik Svensmark, Nir Shaviv antworten

Link zum Paper. Da schaut man mal 3 Tage nicht in die MINT-Ecke der Blogosphäre, und schon geht einem die wichtigste Entdeckung des bisherigen 21. Jhdt.s durch die Lappen.

https://www.nature.com/articles/s41467-017-02082-2



"Les hommes seront toujours fous; et ceux qui croient les guérir sont les plus fous de la bande." - Voltaire

Ulrich Elkmann Offline




Beiträge: 7.340

03.01.2018 01:32
#3 RE: Noch ein Weihnachtsgeschenk. Henrik Svensmark, Nir Shaviv antworten

Und weil wir schon mal dabei sind:

Study: Earth Has A ‘Natural Thermostat’ To Regulate Climate During Extreme Temperature Swings

Zitat von Drudge Report, Jan 1, 2018
PARIS — The possibility of controlling the Earth’s temperature has long led to various experiments by inquisitive scientists, but without great results. Now a recent study found proof for the first time ever of a natural thermostat that helps regulate the planet during extreme temperature swings.

British scientists say they’ve discovered that the preeminent mechanism that allows the Earth to recover from global cooling events is linked to the weathering of rocks. Rocks dissolve by rain and river water during the weathering process, and carbon dioxide is taken from the atmosphere to carbon-rich rocks in nearby waterways. When weathering runs its course, there’s a decrease in carbon dioxide on our planet.
...
“From looking at the relative abundance of lithium isotopes in ocean-derived rocks, we were able to confirm that chemical weathering is the driver of the Earth’s natural thermostat,” explains lead scientist, Dr. Philip Pogge von Strandmann, in a news release. “When there is a warmer climate, there is more weathering, and when it is cooler there is less weathering: this is what you would expect, given that chemical reactions go faster with increasing temperature.”



"Les hommes seront toujours fous; et ceux qui croient les guérir sont les plus fous de la bande." - Voltaire

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