Cosmic Rays=Galactic Cosmic Radiation (GCR)
Solar Wind=Geomagnetic Activity=Interplanetary Magnetic Field (IMF)
Radiant Energy Emitted from the Sun=Total Solar Irradiance (TSI)
w/m^2=watts per square meter
Cloud Condensation Nuclei=CCN
When confronted with about a 0.9 degree C increase in temperature over the past century, we look to the obvious. Aside from the core, which shows no variation in heat output, the Sun is the Earth’s heat source, and it’s the obvious place to turn to explain perceived changes in surface temperature. Yet, we as we investigate this idea, a major problem comes forth. Although observational analysis might imply a correlation between changes in Total Solar Irradiance (a description of the total radiant energy emitted by the sun over all wavelengths), physically, it seems that TSI couldn’t possibly account for the warming experienced since 1900. Radiative output varied only 0.1% over the last solar cycle; this amounts to a mere 0.3 w/m^2 of heat input at the top of the atmosphere. The UN IPCC estimates that the sun can only account for under 0.5 w/m^2 relative to 1750. For comparison, the IPCC suggests that changes in greenhouse gases have had a warming effect of slightly under 2.5 w/m^2 over that same interval.
could be large enough to explain the warming.
1. Galactic cosmic radiation (GCR), produced by galactic activity, constantly bombards the Earth.
3. Cosmic rays ionize the lower atmosphere at altitudes of 35km and below.
4. The ionization of the lower atmosphere creates aerosols from which cloud condensation nuclei (CCN) can form.
5. Low clouds increase albedo and cool the Earth.
So where do GCR originate? Unfortunately for us, GCRs vary in energy, and those with the highest energy are the least understood. At the same time, they are incredibly energetic and very rare. Only about 100 GCRs with extremely high energy have ever been observed. While these GCRs are not relevant to the climate change debate (for now…), I’m going to indulge my curiosity a bit and explain the seemingly predominant theory.
There is no controversy surrounding this phenomenon. As I explained, the solar wind is flow of energetic charged particles that block incoming cosmic radiation; the region in which this occurs is called the shock front. Low-energy cosmic rays are sapped of their energy before they make it into the atmosphere, but the more powerful ones are able to make it past the shock front and into the upper atmosphere. When the cosmic radiation hits the atmosphere, showers of secondary particles (protons, neutrons, and muons) are produced by nuclear collisions. These secondary particles continue to travel through the atmosphere, undergoing more collisions and creating even more particles. Around 16km from sea level, the secondary particles have lost too much energy to continue colliding. Below this, electrons and muons (produced by the highest energy cosmic rays) are responsible for the ionization.
2. Interplanetary Magnetic Field/Solar Wind/Geomagnetic Activity
Here are a few graphs demonstrating the connection between TSI and IMF, along with IMF and related data trends. Note how TSI lags behind IMF by approximately ten years.
In the very beginnings of this theory, it was believed that cosmic ray bombardment would effect cloud formation at all altitudes. Theoretically, there seemed to be no reason that it wouldn’t, and the observational data of high and low clouds seemed to support the idea (mid-altitude clouds showed no correlation with GCR bombardment). Yet, once the data was updated to include more modern data, it was clear that post-1989 data on middle and high clouds showed absolutely no correlation with the decreasing GCR bombardment.
Over the past few decades, GCR is clearly very closely correlated to low cloud cover. Because IMF is a solar phenomenon, it contains TSI’s signal with a ten-year cycle, and because low cloud cover closely follows GCR bombardment (which is inversely related to IMF and TSI (though TSI lags behind)), low cloud cover has a ten-year cycle. During that cycle, low cloud cover varies by ~2%; this is calculated to exert a 1.2w/m^2 forcing on the Earth.
So we’ve established both the physical and theoretical defense for the theory (though, I admit I skimmed over the actual ionization process because I do not understand it fully), but all good theories must stand the scrutiny of experiment.
The 111-page long CLOUD proposal reads,
“The primary scientific goals of the CLOUD experiment are as follows:
1. To study the link between cosmic rays and the formation of large ions, aerosol particles, cloud droplets, and ice crystals.
2. To understand the microphysical mechanisms connecting cosmic rays to changes in
aerosol and cloud particle properties.
3. To simulate the effects of cosmic rays on aerosol and cloud properties under atmospheric conditions.”
So we’ve established the physical mechanisms that drive this theory, but we haven’t yet explored the ramifications of it. By comparing trends in the Earth’s temperature and GCR, it seems to suggest that the solar modulation of cosmic rays could be the primary driver of climate on the decadal scale, the millenial scale, and even the multi-million year scale.
A Cosmic Signal in the Icehouse Cycle
Higher levels of cosmic ray flux seem to correspond with the Icehouse cycle, which is characterized by a 100 million year cycle composed of warm periods (hothouses or greenhouses), when no ice or snow exists on Earth, and icehouses, when the Earth bounces back and forth between today’s climate and ice ages.
To determine if temperature and cosmic ray flux correspond over the past millennium, we need to determine what temperature reconstruction to use. I have written one post (with more to come) criticizing Michael Mann’s “hockey stick” reconstruction for being methodologically unsound, intellectually dishonest, and absolutely corrupted by tricky statistical methods, and in its place, I will use Loehle’s 2007 reconstruction, which uses no tree rings, and every set of data has been peer-reviewed and adjusted for local temperature (a feat that has never been accomplished before in paleoclimatology). Loehle’s reconstruction shows a strong warm signal during the Medieval Warm Period (MWP) (900-1300 AD) and a strong cold signal during the Little Ice Age (LIC) (1400-1850). Cosmic ray bombardment data shows a very strong correlation with these trends; as shown by the graph, during the MWP, GCR bombardment was especially low, and during the LIC, GCR bombardment was especially high. This correlation that implies GCR flux is the dominant force in cloud cover over long time periods came as somewhat of a surprise. It is important to note that temperatures during the coldest part of the LIC follow the same trend as the solar-modulated GCR flux, rather than TSI itself. Although it seemed possible that changes in GCR flux could significantly alter decadal changes in cloud cover, the suggestion that it could dominate multi-decadal, millennial, and even geological cloud cover despite the massive climate forces and cycles at work is unbelievable, yet, at the same time, the evidence is there to confirm it.
In short, it flies in the face of the enhanced greenhouse effect hypothesized by numerous federal agencies, many climate scientists, the UN, and the liberal media. While some warming remains to be explained, the discovery of this cosmic connection lends credibility to the idea that solar variability is a first-order climate forcing. Although I should refrain from making broad, overarching statements, I’m going to go ahead and say that at least 70% of all changes in temperature up until 1980 can be attributed to changes in the solar magnetic field and thus GCR flux. This theory, coupled with increased pollution, even explains the somewhat mysterious global cooling experienced during the post-WW2 era. It is after 1980 that things become slightly more complex. GCR flux, following Solar magnetic field intensity, has continued in its ten-year cycle, but the amplitude of the cycle has remained unchanged, and no upward shift in the cycle has occurred. Over at Real Climate, they claim this as evidence to discredit the entire idea, though they do admit it is an issue that deserves attention. Increasing levels of CO2, global brightening (the reversal of global dimming through the disintegration of post-WW2 aerosol pollutants), and the recent large collective magnitude of the oceanic cycles could all explain recent warming, though increased CO2 levels are most likely playing a greater role in temperature variations.
What does this mean for the future?