Guest spider web log past times Nir Shaviv, originally posted at his websiteShaviv is a prominent Israeli astrophysicist too climate skeptic (formulation past times LM) who also participated at a Cambridge climate debate a calendar month agone (report). Five days ago, Nature Communications published his newspaper written amongst 3 well-known Danish colleagues that argues that the processes allowing cosmic rays to create clouds take hold been understood microscopically, too.
Finally! The missing link betwixt exploding stars, clouds too climate on Earth
By Nir Shaviv too Henrik Svensmark
Our novel results published today inwards nature communications furnish the lastly slice of a long studied puzzle. We finally constitute the actual physical machinery linking betwixt atmospheric ionization too the formation of cloud condensation nuclei. Thus, nosotros straight off empathise the consummate physical motion-picture exhibit linking solar activity too our galactic environs (which principle the flux of cosmic rays ionizing the atmosphere) to climate hither on public though changes inwards the cloud characteristics. In short, every bit little aerosols grow to move cloud condensation nuclei, they grow faster nether higher background ionization rates. Consequently, they take hold a higher endangerment of surviving the growth without existence eaten past times larger aerosols. This consequence was calculated theoretically too measured inwards a particularly designed experiment conducted at the Danish Space Research Institute at the Danish Technical University, together amongst our colleagues Martin Andreas Bødker Enghoff too Jacob Svensmark.
Background
It has long been known that solar variations look to take hold a large consequence on climate. This was already suggested past times William Herschel over 200 years ago. Over the past times several decades, to a greater extent than empirical evidence take hold unequivocally demonstrated the existence of such a link, every bit exemplified inwards the examples inwards the box below.
The fact that the body of body of water sea grade changes amongst solar activity (see Box 1 above) clearly demonstrates that at that topographic point is a link betwixt solar activity climate, but it tin live used to quantify the solar climate link too exhibit that it is real large. In fact, this “calorimetric” criterion of the solar radiative forcing is most 1 to 1.5 W/m2 over the solar cycle, compared amongst the 0.1-0.2 W/m2 modify expected from simply changes inwards the solar irradiance. This agency that a machinery amplifying solar activity should live operating—the Sun has a much larger consequence on climate than tin live naively expected from simply changes inwards the solar output.
Over the years, a duet of mechanisms were suggested to explicate the large solar climate link. However, i detail machinery has accumulated a meaning amount of evidence inwards its support. The machinery is that of solar air current modulation of the cosmic rays, which principle the amount of atmospheric ionization, too which inwards plough impact the formation of cloud condensation nuclei too thus how much calorie-free do the clouds reverberate dorsum to space, every bit nosotros straight off explain.
Cosmic Rays are high unloose energy particles originating from supernova remnants. These particles diffuse through the Milky Way. When they attain the solar arrangement they tin diffuse into the inner parts (where public is) but lose some unloose energy along the way every bit they interact amongst the solar wind. Here on public they are responsible for most of the ionization inwards the Troposphere (the lower 10-20 km of the atmosphere where most of the “weather” takes place). We straight off know that this ionization plays a purpose inwards the formation of cloud condensation nuclei (CCNs). The latter are little (typically 50nm or larger) aerosols upon which H2O vapor tin condense when saturation (i.e., 100% humidity) is reached inwards the atmosphere. Since the properties of clouds, such every bit their lifetime too reflectivity, depends on the issue of CCNs, changing the CCNs formation charge per unit of measurement volition impact Earth’s unloose energy balance.
The total link is thus every bit follows: H5N1 to a greater extent than active Sun implies a lower CR flux reaching public too amongst it, lower ionization. This inwards plough implies that fewer cloud condensation nuclei are produced such that the clouds that subsequently cast alive shorter lives too are less white, thereby allowing to a greater extent than solar radiations to exceed through too warm our planet.
Figure 5: The link betwixt solar activity too climate: H5N1 to a greater extent than active Sun reduces the amount of cosmic rays coming from supernovae around us inwards the galaxy. The cosmic rays are the dominant source of atmospheric ionization. It turns out that these ions play an of import purpose inwards (a) increasing the nucleation of little condensation nuclei (a few nm) too (b) increasing the growth charge per unit of measurement of the condensation nuclei (which is the consequence simply published). The larger growth rates imply that they are less probable to stick to pre-existing aerosols too thus take hold a larger endangerment of reaching the sizes of cloud condensation nuclei (CCNs, typically over 50 nm inwards diameter). Thus, a to a greater extent than active Sun decreases the formation of CCNs, making the clouds less white, reflecting less sunlight too thus warming Earth.
Until today nosotros had simply empirical results which demonstrate that this link is indeed taking place. The primary results are summarized inwards Box 2 below. In particular, nosotros take hold seen correlations betwixt solar activity too cloud comprehend variations, every bit good every bit betwixt cosmic ray flux variations arising from changes inwards our galactic environs too long term climate modify using geological data.
Box 2: Examples showing the cosmic ray climate link
The commencement empirical evidence linking solar activity amongst cloud comprehend was the correlation betwixt solar activity (as proxied past times the cosmic rays) too changing cloud comprehend (Svensmark & Friis-Christensen 1997), inwards particular, the depression height cloud comprehend (see Marsh & Svensmark 2000). Although subsequently information has cross-satellite calibration problems, the correlation continued. Interestingly, Cosmic rays exhibit an odd/even asymmetry because they are the solely solar modulated ingredient that “sees” the fact that subsequent solar cycles take hold contrary magnetic patch polarity. The cloud comprehend appears to exhibit the same asymmetry.
Figure 6: The correlation betwixt depression height cloud comprehend (blue) too the cosmic ray flux reaching basis (red).
Later, to a greater extent than evidence for the fact that cosmic rays are non solely the proxy of solar activity but are an actual share of the climate machinery appeared inwards the cast of correlations betwixt cosmic ray flux variations that take hold nix to do amongst solar activity too climate variations. Such variations inwards the cosmic ray flux leave of absence over geological fourth dimension scales. We showed that i tin utilization Iron meteorites to reconstruct the cosmic ray flux variations over the past times billion years. These variations exhibit 7 increases due to passages through the galactic spiral arms, on i hand, but look to correlate amongst the appearance of H2O ice historic menstruation epochs on Earth, on the other (Shaviv, 2002, Shaviv 2003, Shaviv & Veizer 2003). Clearly, cosmic ray flux variations that are independent of solar activity look to take hold a large consequence on climate every bit well.
The commencement empirical evidence linking solar activity amongst cloud comprehend was the correlation betwixt solar activity (as proxied past times the cosmic rays) too changing cloud comprehend (Svensmark & Friis-Christensen 1997), inwards particular, the depression height cloud comprehend (see Marsh & Svensmark 2000). Although subsequently information has cross-satellite calibration problems, the correlation continued. Interestingly, Cosmic rays exhibit an odd/even asymmetry because they are the solely solar modulated ingredient that “sees” the fact that subsequent solar cycles take hold contrary magnetic patch polarity. The cloud comprehend appears to exhibit the same asymmetry.
Figure 6: The correlation betwixt depression height cloud comprehend (blue) too the cosmic ray flux reaching basis (red).
Later, to a greater extent than evidence for the fact that cosmic rays are non solely the proxy of solar activity but are an actual share of the climate machinery appeared inwards the cast of correlations betwixt cosmic ray flux variations that take hold nix to do amongst solar activity too climate variations. Such variations inwards the cosmic ray flux leave of absence over geological fourth dimension scales. We showed that i tin utilization Iron meteorites to reconstruct the cosmic ray flux variations over the past times billion years. These variations exhibit 7 increases due to passages through the galactic spiral arms, on i hand, but look to correlate amongst the appearance of H2O ice historic menstruation epochs on Earth, on the other (Shaviv, 2002, Shaviv 2003, Shaviv & Veizer 2003). Clearly, cosmic ray flux variations that are independent of solar activity look to take hold a large consequence on climate every bit well.
The commencement proposition for an actual physical machinery was that ions increment the nucleation of little (2-3 nm sized) aerosols called condensation nuclei (CNs). The thought is that little clusters of sulfuric acid too H2O (the primary edifice blocks of little aerosols) are much to a greater extent than stable if they are charged. That is, the accuse allows the aerosols to grow from a real little (few molecule) cluster to a little stable CN without breaking apart inwards the process. This consequence was commencement seen inwards our lab (Svensmark 2006). The consequence was seen in i lawsuit again inwards the CLOUD experiment running at CERN (Kirkby 2011). Later experiments take hold shown that ions accelerate also other nucleation routes inwards which the little clusters are stabilized past times a 3rd molecule (such every bit Ammonia). That is, ions play a dominant purpose inwards accelerating almost all nucleation routes (as long every bit the total nucleation charge per unit of measurement is lower than the ion formation rate).
Figure 7: The Ion induced nucleation consequence measured inwards the lab. Left: The commencement demonstration inwards our SKY experiment showing that increased ionization increases the nucleation of little aerosols (typically 3 nm inwards size). Right: Corroboration of the results inwards the CLOUD experiment at CERN.
In the meantime, a issue of enquiry groups aimed at testing the thought that cosmic ray ionization could attention the formation of cloud condensation nuclei (CCN). This was done past times using large global circulation models coupled amongst aerosol physics. The thought was to run into if an added issue of little aerosols would grow into to a greater extent than CCNs. All of the numerical models gave the resultant that the little aerosols were lost earlier they could move large enough, leading to the determination that the consequence of cosmic rays on the issue of CCN over a solar wheel was insignificant (e.g., Pierce too Adams 2009). This could also live explained analytically (Smith et al. 2016). It was thus proclaimed that the theory was dead.
Given the empirical evidence, it was clear to us that a link must live present, fifty-fifty if the ion induced nucleation machinery itself is insufficient to explicate the link. Thus, our reply was to address the same interrogation without using models but instead to assay it experimentally. Therefore, inwards 2012 nosotros tested if little nucleated aerosols could grow into CCN inwards our laboratory too discovered that without ions present, the reply to increased nucleation was severely damped, simply similar the above-mentioned models; nevertheless amongst ions present, all the extra nucleated particles grew to CCN sizes, inwards contrast to the numerical model results (Svensmark et al. 2013). So, experiments contradicted the models. The logical determination was that some unknown ion-mechanism is operating, helping the growth.
Figure 8: Left: When injecting little aerosols, the relative increment decreases amongst aerosol size because every bit aerosols grow they tend to coagulate amongst larger aerosols. Right: However, when increasing the ionization inwards the chamber, non solely are to a greater extent than aerosols nucleated, the relative increment survives to larger sizes implying that some machinery is increasing the survivability of the aerosols every bit they grow.
Following the experimental results showing that increased ionization does indeed increment the issue of large CCNs, the natural interrogation to inquire was whether these results were caused past times the detail experimental conditions—perhaps this machinery does non function inwards the existent atmosphere. It is thus fortunate that our Lord's Day carries out natural experiments amongst the whole Earth.
On rare occasions, “explosions” on the Lord's Day called coronal majority ejections resultant inwards a plasma cloud passing the Earth, amongst the consequence that the cosmic rays flux decreases all of a abrupt too remains depression for most a week. Such events, amongst a meaning reduction inwards the cosmic ray flux, are called Forbush decreases, too are ideal to assay the link betwixt cosmic rays too clouds. Finding the strongest Forbush decreases too using 3 independent cloud satellite datasets too i dataset for aerosols, nosotros clearly constitute a reply to Forbush decreases. These results validated the whole chain from solar activity, to cosmic rays, to aerosols (CCN), too finally to clouds, inwards Earth’s atmosphere (Svensmark et al 2009, Svensmark et al. 2016).
Figure 9: The average consequence of the v strongest Forbush decreases inwards the 1987-2007 menstruation on cloud properties. Plotted inwards cherry is the reduction inwards the cosmic ray flux next “gusts” inwards the solar air current (from Coronal Mass Ejections). In dark nosotros run into the reduction inwards aerosols over the oceans too 3 dissimilar cloud parameters from 3 dissimilar datasets (Svensmark et al 2009). These results furnish an inwards situ demonstration of the consequence of cosmic rays on aerosols too cloud properties.
With the accumulating empirical too experimental evidence, it was clear that atmospheric ionization is playing a purpose inwards the generation of the aerosols needed for cloud formation, however, the exact machinery proved to live elusive. For this reason, nosotros decided to setup some other laboratory experiment mimicking conditions constitute inwards the existent atmosphere too study how atmospheric ions may live affecting the production of CCNs. This also led us to expression for choice mechanisms which volition increment the survivability of the CNs every bit they growth. Indeed, after several years of research, i was found.
The discovery
H5N1 niggling to a greater extent than than 2 years ago, nosotros made the realization that accuse volition play a purpose inwards accelerating the growth charge per unit of measurement of little aerosols. When to a greater extent than ions are introduce inwards the atmosphere, to a greater extent than of them halt upwardly sitting on sulfuric acid clusters of a few molecules. Moreover, the accuse makes the sulfuric acid clusters stick to the growing aerosols much faster, every bit nosotros explicate inwards the box below. Since faster growing aerosols take hold lower chances of coagulating amongst larger aerosols, to a greater extent than of the growing aerosols tin too so last to attain larger sizes. In other words, when the ionization charge per unit of measurement is higher, to a greater extent than CCNs tin are formed.
Box 3: The physics behind the novel mechanism
The physics responsible for the accelerated growth is genuinely relatively simple. H5N1 charged cluster of a few molecules of sulfuric acid too H2O volition cause a polarization on the growing aerosols—charge volition motion from i side of the aerosol to the other, such that i side volition live positively charged, patch the other negatively charged (with no internet charging of the aerosols). Through interaction amongst this polarization (called Debye force), the cluster too aerosols are attracted. This agency that charged clusters stick onto the aerosols notably faster than neutral clusters. Thus, when to a greater extent than ions are present, aerosols tin grow faster, too if so, the probability that they stick onto larger aerosols (and thus lost from the system) is smaller.
Figure 10: H5N1 negatively charged cluster induces a polarization of the neutral aerosol too and so gets attracted to it (since the line from the positive side of the aerosol is stronger than the force from the negative side).
The physics responsible for the accelerated growth is genuinely relatively simple. H5N1 charged cluster of a few molecules of sulfuric acid too H2O volition cause a polarization on the growing aerosols—charge volition motion from i side of the aerosol to the other, such that i side volition live positively charged, patch the other negatively charged (with no internet charging of the aerosols). Through interaction amongst this polarization (called Debye force), the cluster too aerosols are attracted. This agency that charged clusters stick onto the aerosols notably faster than neutral clusters. Thus, when to a greater extent than ions are present, aerosols tin grow faster, too if so, the probability that they stick onto larger aerosols (and thus lost from the system) is smaller.
Figure 10: H5N1 negatively charged cluster induces a polarization of the neutral aerosol too and so gets attracted to it (since the line from the positive side of the aerosol is stronger than the force from the negative side).
After realizing that this consequence should live taking house nosotros did 2 things. First, nosotros calculated how large it should live too constitute that for the typical conditions introduce inwards the pristine air to a higher house oceans, inwards which the typical sulfuric acid density is a few 106 molecules/cm3, the ions accelerate the growth past times typically 1 to 4%. However, because the issue of aerosols surviving the growth is exponentially little (typically several e-folds), the relative modify inwards the CCN density is a few times larger silent (by the issue of e-folds inwards the exponential damping to live precise). Thus, over the solar wheel (which changes the tropospheric ionization past times typically 20%), nosotros await a several percent variation inwards the CCN density too amongst it, the cloud properties, every bit is observed.
The minute affair nosotros did was move to the lab too blueprint an experiment inwards which nosotros tin run into this consequence taking house (and also validate our theoretical calculations). This is non trivial because the consequence is larger for lower sulfuric acid levels (as a larger percent of the molecules would live charged). However nosotros cannot stair out at real depression sulfuric acid levels because the aerosols too so grow real tardily such that they stick to the bedchamber walls earlier their growth tin live reliably measured. This forced us to stair out at high sulfuric acid levels for which the consequence is smaller. This posed a formidable technological challenge. To overcome this, nosotros designed an experiment which tin maintain relatively stable conditions over long periods (up to several weeks at a time) during which nosotros could automatically increment or decrease the ionization charge per unit of measurement at the chamber. This allowed us to collect a large amount of information too larn high character signals (e.g., run into fig. xi inwards the box below).
We constitute that aerosols indeed grow faster when the ionization charge per unit of measurement is higher, totally consistent amongst the theoretical predictions (as tin live seen inwards fig. 12 inwards the box below). This allows them to last the growth menstruation without coagulating amongst larger aerosols.
Box 4: Sample Results
Although the reader is tin read the article online, hither are a few sample results.
Figure 11: The growth of aerosols inwards the experiment. Lower panel: Color coded is the issue density of aerosols every bit a share of fourth dimension (horizontal axis), too diameter of aerosols inwards nm (vertical axis). Every 2 hours the γ-ray sources are opened/closed. Thus, share of the growth is amongst high ionization too share amongst depression such that the growth rates tin live compared. Top: Since the differences are non large nether the experimental conditions, the ionizing sources tin live switched on/off over many cycles to larn high character statistics. The ground that the indicate is little inwards the experiment is because growth inwards the bedchamber has to live an club of magnitude faster than inwards the atmosphere, otherwise the aerosols would stick to the bedchamber walls. Under the faster growth conditions, the consequence is smaller.
Figure 12: Difference inwards the γ-ray opened upwardly too unopen growth times (from half dozen to 12 nm), inwards xi runs amongst dissimilar sulfuric acid densities (and thus growth rates) too dissimilar modify inwards ionization. The dashed lines are the theoretical predictions.
Although the reader is tin read the article online, hither are a few sample results.
Figure 11: The growth of aerosols inwards the experiment. Lower panel: Color coded is the issue density of aerosols every bit a share of fourth dimension (horizontal axis), too diameter of aerosols inwards nm (vertical axis). Every 2 hours the γ-ray sources are opened/closed. Thus, share of the growth is amongst high ionization too share amongst depression such that the growth rates tin live compared. Top: Since the differences are non large nether the experimental conditions, the ionizing sources tin live switched on/off over many cycles to larn high character statistics. The ground that the indicate is little inwards the experiment is because growth inwards the bedchamber has to live an club of magnitude faster than inwards the atmosphere, otherwise the aerosols would stick to the bedchamber walls. Under the faster growth conditions, the consequence is smaller.
Figure 12: Difference inwards the γ-ray opened upwardly too unopen growth times (from half dozen to 12 nm), inwards xi runs amongst dissimilar sulfuric acid densities (and thus growth rates) too dissimilar modify inwards ionization. The dashed lines are the theoretical predictions.
So, what do the results imply? Until straight off nosotros had meaning amount of empirical evidence which demonstrated that cosmic rays impact climate, but nosotros didn't take hold the actual underlying physical machinery pinned down. Now nosotros have. It agency that nosotros non solely run into the existence of a link, nosotros straight off empathise it. Thus, if the solar activity climate link was until straight off ignored nether the pretext that it cannot live real, this volition take hold to change. But mayhap to a greater extent than interestingly, it also explains how long term variations inwards our galactic environs halt upwardly affecting our climate over geological fourth dimension scales.
Box 5: Why is the CR/climate link ignored?
Given all the empirical evidence that has accumulated until now, the climate community should take hold considered it seriously, too fifty-fifty if the actual machinery was until straight off missing, the empirical evidence showing too quantifying the solar climate link shouldn’t take hold been ignored past times most of the community.
The ground is genuinely real uncomplicated too lays inwards the implication of the link. If the Sun has a large consequence on climate, too so its increment activity over the 20th century should take hold contributed at to the lowest degree some of the global warming. In fact, the calorimetric sea grade based measurements imply that a flake to a greater extent than than one-half of the 20th century warming should live attributed to the sun. If so, the purpose that humans take hold had is diminished. In fact, when i considers the purpose that the Sun has had over the 20th century, i finds that a) the temperature variations tin genuinely live much ameliorate explained (with a smaller residual) too the required climate sensitivity is on the depression side (about 1 to 1.5°C increment per CO2 doubling, compared amongst the canonical hit of 1.5 to 4.5°C advocated past times the IPCC, run into Ziskin & Shaviv 2012). The depression climate sensitivity implies that the same emission scenarios volition give ascent to to a greater extent than pocket-sized temperature increases over the 21st century. These practiced tidings imply that nosotros are non inwards every bit dire a situations every bit nosotros ofttimes hear. But many do non similar hearing this.
Now that the machinery is genuinely known, at that topographic point should live no excuse inwards ignoring it whatever further, but given the to a higher house implications, it would most probable silent live ignored.
Given all the empirical evidence that has accumulated until now, the climate community should take hold considered it seriously, too fifty-fifty if the actual machinery was until straight off missing, the empirical evidence showing too quantifying the solar climate link shouldn’t take hold been ignored past times most of the community.
The ground is genuinely real uncomplicated too lays inwards the implication of the link. If the Sun has a large consequence on climate, too so its increment activity over the 20th century should take hold contributed at to the lowest degree some of the global warming. In fact, the calorimetric sea grade based measurements imply that a flake to a greater extent than than one-half of the 20th century warming should live attributed to the sun. If so, the purpose that humans take hold had is diminished. In fact, when i considers the purpose that the Sun has had over the 20th century, i finds that a) the temperature variations tin genuinely live much ameliorate explained (with a smaller residual) too the required climate sensitivity is on the depression side (about 1 to 1.5°C increment per CO2 doubling, compared amongst the canonical hit of 1.5 to 4.5°C advocated past times the IPCC, run into Ziskin & Shaviv 2012). The depression climate sensitivity implies that the same emission scenarios volition give ascent to to a greater extent than pocket-sized temperature increases over the 21st century. These practiced tidings imply that nosotros are non inwards every bit dire a situations every bit nosotros ofttimes hear. But many do non similar hearing this.
Now that the machinery is genuinely known, at that topographic point should live no excuse inwards ignoring it whatever further, but given the to a higher house implications, it would most probable silent live ignored.
Below are several examples showing that the Sun has a large consequence on climate. The commencement illustration is the beautiful correlation betwixt solar activity (as mirrored inwards the Carbon 14 extracted from tree rings) too Oxygen eighteen to Oxygen sixteen isotope ratio is stalagmites inwards a cave inwards Oman, measured past times Neff et al. (2001). The one-time is a proxy of solar activity (as the solar air current modulates the flux of cosmic rays reaching the terrestrial atmosphere too producing Carbon xiv through spallation). Oxygen 18 is a good known climate proxy (in this case, of the monsoon pelting coming from the Indian ocean). [I replaced the Apple link amongst the Wikipedia one.]
Figure 1: H5N1 correlation betwixt 14C/12C from tree rings (a proxy of solar activity) too 18O/16O from stalagmites inwards a cave inwards Sultanate of Oman inwards the southern Arabian peninsula past times Neff et al. (2001) (which is a proxy of the temperature of the Indian ocean). H5N1 large correlation is apparent.
The minute example, past times Bond et al. (2001), shows a clear correlation betwixt solar activity (again every bit recovered using 14C) too the climate of the North Atlantic, every bit tin live reconstructed from H2O ice rafted debris inwards cores from the body of body of water floor.
Figure 2: H5N1 correlation betwixt 14C/12C from tree rings (a proxy of solar activity) too the amount of H2O ice rafted debris left on the body of body of water flooring inwards the Northern Atlantic. Again, a large correlation is apparent.
The 3rd example, on shorter fourth dimension scales, is the clear correlation betwixt solar activity over the past times century, exhibiting the quasi periodic xi twelvemonth solar cycle, too the charge per unit of measurement of modify of the sea level.
Figure 3: The correlation betwixt solar activity (in red) too the sea grade charge per unit of measurement of modify from tide gauges across the globe.
Unlike the previous results which qualitatively demonstrate the existence of a rigid solar/climate link, the lastly correlation, past times Shaviv (2008), tin live used to quantify the link too exhibit that the solar minimum to solar maximum variations inwards the solar activity translates into a 1 to 1.5 W/m2 modify inwards Earth’s unloose energy budget. H5N1 to a greater extent than recent analysis of satellite altimetry information reveals that the correlation continues. In fact, if i removes the linear tendency from glacier melting, almost all the sea grade modify tin live attributed to the Sun too the el Niño southern oscillation (Howard et al. 2015).
Figure 4: The correlation betwixt the linearly detrended sea grade measured using satellite altimetry (blue dots) too a model gibe which includes simply 2 components: The Sun too el Niñoo southern oscillation. The first-class gibe implies that the 2 components are past times far the dominant source of sea grade modify on brusque fourth dimension scales