Those who are fond of using the phrase "climate change denier" have attacked HS in the past and probably will now. I think HS's work likely has much to do with the truth.
It seems likely to me that the "official" view of climate change does not reflect the limitations of both the popular models and data. Do you think the models are "complete"? Are they statistical, mathematical (e.g., differential equation based"? If based on differential equations, are they linear or non linear? If non-linear, which is likely to be closer to the truth, how come you don't hear about "strange attractors"?
Here are some excerpts from HS's paper.
-------------------------------------------
EXECUTIVE SUMMARY
Over the last twenty years there has been good progress in understanding the solar influence on climate. In particular, many scientific studies have shown that changes in solar activity have impacted climate over the whole Holocene period (approximately the last 10,000 years). A well-known example is the existence of high solar activity during the Medieval Warm Period, around the year 1000 AD, and the subsequent low levels of solar activity during the cold period, now called The Little Ice Age (1300–1850 AD). An important scientific task has been to quantify the solar impact on climate, and it has been found that over the elevenyear solar cycle the energy that enters the Earth’s system is of the order of 1.0–1.5 W/m2. This is nearly an order of magnitude larger than what would be expected from solar irradiance alone, and suggests that solar activity is getting amplified by some atmospheric process. Three main theories have been put forward to explain the solar–climate link, which are: • solar ultraviolet changes • the atmospheric-electric-field effect on cloud cover • cloud changes produced by solar-modulated galactic cosmic rays (energetic particles originating from inter stellar space and ending in our atmosphere). Significant efforts has gone into understanding possible mechanisms, and at the moment cosmic ray modulation of Earth’s cloud cover seems rather promising in explaining the size of solar impact. This theory suggests that solar activity has had a significant impact on climate during the Holocene period. This understanding is in contrast to the official consensus from the Intergovernmental Panel on Climate Change, where it is estimated that the change in solar radiative forcing between 1750 and 2011 was around 0.05 W/m2, a value which is entirely negligible relative to the effect of greenhouse gases, estimated at around 2.3 W/m2. However, the existence of an atmospheric solar-amplification mechanism would have implications for the estimated climate sensitivity to carbon dioxide, suggesting that it is much lower than currently thought. In summary, the impact of solar activity on climate is much larger than the official consensus suggests. This is therefore an important scientific question that needs to be addressed by the scientific community.
INTRODUCTION
The Sun provides nearly all the energy responsible for the dynamics of the atmosphere and oceans, and ultimately for life on Earth. However, when it comes to the observed changes in our terrestrial climate, the role of the Sun is not uniformly agreed upon. Nonetheless, in climate science an official consensus has formed suggesting that the effect of solar activity is limited to small variations in total solar irradiance (TSI), with insignificant consequences for climate. This is exemplified in the reports of Working Group I of the Intergovernmental Panel on Climate Change (IPCC), who estimate the radiative forcing on climate from solar activity between 1750 and 2011 at around 0.05 W/m2. This value is entirely negligible compared to changes in anthropogenic greenhouse gases, whose forcing is estimated at around 2.3 W/m2. 1 The aim of this report is to give a review of research related to the impact of solar activity on climate. Contrary to the consensus described above, there is abundant empirical evidence that the Sun has had a large influence on climate over the Holocene period, with temperature changes between periods of low and high solar activity of the order of 1–2 K. Such large temperature variations are inconsistent with the consensus and herald a real and solid connection between solar activity and Earth’s climate. The question is: what is the mechanism that is responsible for the solar–climate link? A telling result is given by the energy that enters the oceans over the 11-year solar cycle, which is almost an order of magnitude larger (∼1–1.5 W/m2) than the corresponding TSI variation (∼0.2 W/m2). Solar activity is somehow being amplified relative to the TSI variations by a mechanism other than TSI. There are other possible drivers of these changes: solar activity also manifests itself in components other than TSI. These include large relative changes in its magnetic field, the strength of the solar wind (the stream of charged particles that carries the magnetic field), modulation of cosmic ray ionisation in the Earth’s atmosphere, and the amount of ultraviolet (UV) radiation, to name a few. All of these are part of what is referred to as ‘solar activity’, and all have been suggested to influence climate as well. In particular, it will be shown that a mechanism has been identified that can explain the observed changes in climate, and which is supported by theory, experiment and observation. This report is not meant to be an exhaustive representation of all the published papers related to a solar influence on Earth’s climate, but aims to give a clear presentation of the current knowledge on the link between solar activity and climate. A comprehensive review of the Sun’s impact on climate was published previously, 2 but is now eight years old; important progress on the mechanism linking solar activity and climate has been made since. Technical material will not be included in the report, but rather reference will be made to the literature in the field so that the interested reader can find further information.COSMIC RAY CLOUDS MECHANISM
Another possible mechanism is changes to Earth’s cloud cover due to solar modulation of cosmic rays. 50–52 In 1996, satellite observations showed that Earth’s cloud cover changed by around 2%, in phase with changes in cosmic rays, over a solar cycle. Such a variation corresponds to a change in radiative forcing of around 1 W/m2, which would be in agreement with the observed changes in energy entering the oceans (see Figure 9). The fundamental idea is that cosmic ray ionisation in the atmosphere is important for the formation and growth of small aerosols into CCN, which are necessary for the formation of cloud droplets and thereby clouds. Changing the number density of CCN changes the cloud microphysics, which in turn changes both the radiative properties and the lifetime of clouds (see Figure 12). There is now theoretical, experimental and observational evidence to support the cosmic ray–cloud link, although it should be mentioned that satellite observations of cloud changes on 11-year timescales are by no means entirely reliable due to inherent calibration problems. However, in support of the theory, the whole link from solar activity, to cosmic ray ionisation to aerosols to clouds, has been observed in connection with Forbush decreases on timescales of a week. The cosmic ray variations in response to the stronger Forbush decreases are of similar size to the variations seen over the 11-year solar cycle and result in a change in cloud cover of approximately 2%. Cloud variations are one of the most difficult and uncertain features of the climate system, and therefore cosmic rays and their effect on clouds will add important new understanding of this area. There have been attempts to include the effect of ionisation on the nucleation of small aerosols in large numerical models, but important physical processes are missing. Although there are uncertainties in all of the above observations, they collectively give a consistent picture, indicating an effect of ionisation on Earth’s cloud cover, which in turn can strongly influence climate and Earth’s temperature. Nonetheless, the idea of a cosmicray link to climate has been questioned, and can still give rise to debate. But as more data from observations and experiments are obtained, the case for the link has only become stronger. For example, if the cosmic ray–climate link is real, then any variation of the cosmic ray flux, including those which have nothing to do with solar activity, will translate into changes in the climate as well. Over geological timescales, large variations in the cosmic ray flux arise from the changing galactic environment around the solar system. A comparison between reconstructions of the cosmic ray flux and climate over these long timescales demonstrates that, over the past 500 million years, ice ages have arisen in periods when the cosmic ray flux was high, as the theory predicts. Even the solar system’s movement in and out of the galactic plane can be observed in the climate record.
CONCLUSION
Over the last 20 years, much progress has been made in understanding the role of the Sun in the Earth’s climate. In particular, the frequent changes between states of low and high solar activity over the last 10,000 years are clearly seen in empirical climate records. Of these climate changes, the best known are the Medieval Warm Period (950–1250 AD) and the Little Ice Age (1300–1850 AD), which are associated with a high and low state of solar activity, respectively. The temperature change between the two periods is of the order of 1.0–1.5 K. This shows that solar activity has had a large impact on climate. The above statement is in direct contrast to the IPCC, which estimates the solar forcing over the 20th century as only 0.05 W/m2, which is too small to have a climatic effect. One is therefore left with the conundrum of not having an explanation for the difference in climate between the Medieval Warm Period and Little Ice Age. But this result is obtained by restricting solar activity to only minute changes in total solar irradiance. There are other mechanisms by which solar activity can influence climate. One mechanism is based on changes in solar UV radiation. However, the conclusion seems to be that the effect of UV changes is too weak to explain the energy that enters the oceans over the solar cycle. In contrast, the amplification of solar activity by cosmic ray ionisation affecting cloud cover has the potential to explain the observed changes. This mechanism is now supported by theory, experiment, and observations. Sudden changes in cosmic ray flux in connection with Forbush decreases allow us to see the changes in each stage along the chain of the theory: from solar activity, to ionisation changes, to aerosols, and then to cloud changes. In addition, the impact of cosmic rays on the radiative budget is found to be an order of magnitude larger than the TSI changes. Additional support for a cosmic ray–climate connection is the remarkable agreement that is seen on timescales of millions and even billions of years, during which the cosmic ray flux is governed by changes in the stellar environment of the solar system; in other words, it is independent of solar activity. This leads to the conclusion that a microphysical mechanism involving cosmic rays and clouds is operating in the 20 Earth’s atmosphere, and that this mechanism has the potential to explain a significant part of the observed climate variability in relation to solar activity. An open question is how large secular changes in total solar irradiance can be. Current estimates range from 0.1% to outlier estimates of 0.5%; the latter would be important for climate variation. A small TSI variation, on the other hand, would mean that TSI is not responsible for climate variability. Perhaps future observations will be able to constrain TSI variability better. Climate science in general is, at present, highly politicised, with many special interests involved. It should therefore be no surprise that the above conclusion on the role of the Sun in climate is strongly disputed. The core problem is that if the Sun has had a large influence over the Holocene period, then it should also have had a significant influence in the 20th century warming, with the consequence that the climate sensitivity to carbon dioxide would be on the low side. The observed decline in solar activity would then also be responsible for the observed slowing of warming in recent years. Needless to say, more research into the physical mechanisms linking solar activity to climate is needed. It is useless to pretend that the problem of solar influence has been solved. The single largest uncertainty in determining the climate sensitivity to either natural or anthropogenic changes is the effect of clouds, and research into the solar effect on climate will add significantly to understanding in this area. Such efforts are only possible by acknowledging that this is a genuine and important scientific problem and by allocating sufficient research funds to its investigation.
No comments:
Post a Comment