by Javier Vinós & Andy May
“On the other hand, I think I can safely say that nobody understands climate change.”
J. Vinós, paraphrasing Richard Feynman’s words about quantum mechanics.
This unplanned plain-language summary has been written at the request of some readers of our series of articles on the Winter Gatekeeper hypothesis:
Climate is extremely complex, and people, including scientists, have a natural tendency to look for simple explanations. The Occam’s Razor principle is a good first approach, but climate change cannot have a simple answer. Over the past seven years, one of the authors of this series (JV) has been laboriously reading many thousands of scientific articles and analyzing hundreds of climate datasets trying to understand how Earth’s climate changes naturally. This is a first step to understanding the human impact on climate change. The outcome of this work is the book “Climate of the Past, Present and Future.” It is a graduate-student level academic book that discusses many controversial issues about natural climate change over the past 800,000 years. In this book, a new hypothesis on natural climate change is presented. It relates changes in the strength of the meridional (poleward) transport of energy with climatic changes that have taken place, both in the past and recently.
Since meridional transport is most variable during the winter of the Northern Hemisphere, and is modulated by solar activity, we named the concept the Winter Gatekeeper hypothesis. The other author of the series (AM) is a writer of several published climate books, they are: “Climate Catastrophe! Science or Science Fiction?,” “Politics and Climate Change: A History,” and “The Great Climate Change Debate: Karoly v Happer.” We joined forces to explain this new hypothesis through this series and a new book we are co-writing that will be tailored toward a more general audience. An audience interested in climate change but not in its complex scientific details. The hypothesis grew out of an investigation into the effect of solar variability on climate. But solar variability turned out to be only part of natural climate change. As the scientific evidence for the hypothesis was presented in the first six parts of the series, this summary will present only the conclusions, some additional supporting evidence, and answer a few interesting questions and comments from readers.
7.2 A synopsis of the Winter Gatekeeper hypothesis
The IPCC assessment reports published since 1990, reflect a scientific consensus that natural forces, including solar activity and ocean-atmosphere oscillations, like the Atlantic and Pacific multidecadal oscillations, had a net zero effect on the observed global average surface temperature changes since 1951. The IPCC consensus does not believe changes in the poleward (meridional) transport of energy have significantly affected this average temperature over the past 75 years.
The Winter Gatekeeper hypothesis proposes that changes in the meridional transport of energy and moisture are the main way the climate changes now and in the past. Meridional transport variability has many causes and forces that act simultaneously and in different time frames on the climate system. They integrate into a very complex poleward energy transportation system. Among these are multidecadal ocean-atmosphere oscillations, solar variability, ozone, stratospheric-reaching tropical volcanic eruptions, orbital changes, and changing luni-solar gravitational pull. Meridional transport is therefore an integrator of internal and external signals. It is not the only way the climate changes, but evidence suggests it is the main one.
The Winter Gatekeeper hypothesis does not disprove greenhouse gas effect induced climate change—manmade or otherwise—in fact, it acts through it. But it does not require changes in the atmospheric content of non-condensing greenhouse gases to cause significant climate change. Therefore, it does refute the hypothesis that CO2 is the main climate change control knob.
Meridional transport moves energy that is already in the climate system toward its exit point at the top of the atmosphere at a higher latitude. It is carried out mainly by the atmosphere, in both the stratosphere and troposphere, with an important oceanic contribution. The greenhouse effect is not homogeneous over the planet due to the unequal distribution of water vapor, and it is stronger in the wet tropics, weaker over deserts, and much weaker at the poles in winter. When meridional transport is stronger, more energy reaches the poles. There it can more efficiently exit the climate system, particularly during the winter, when there is no Sun in the sky. Most polar imported moisture in winter freezes, emitting its latent heat. Additional CO2 molecules increase outward radiation, as they are warmer than the surface. The net result is that all imported energy into the polar regions in winter exits the climate system at the top of the atmosphere (Peixoto & Oort, 1992, p. 363), and increasing the energy transported there at that time can only increase the loss.
When meridional transport is stronger, the planet loses more energy and cools down (or warms less) in a non-homogeneous way, because the net energy loss is greater in the polar regions. However, as more energy is directed toward the poles, the Arctic region warms, even as the rest of the world cools or warms more slowly. When meridional transport is weaker, less energy reaches the poles and exits the climate system. Then the planet loses less energy and warms, while the Arctic cools, because it receives less energy from the lower latitudes.
Most of the energy is transported through the lower troposphere and ocean track. As a result, changes in multidecadal ocean oscillations produce a greater effect on climate in the multidecadal timeframe than changes in solar activity. Solar changes have a stronger effect on stratospheric energy transport. Even so, there is a non-well defined link between changes in solar activity and changes in the multidecadal oscillations that result in major multidecadal climate shifts right after 11-year solar cycle minima (see Part IV). Nevertheless, modern global warming started c. 1850, when the Atlantic Multidecadal Oscillation increased its amplitude and period (Moore et al. 2017). The overall multidecadal oscillation (aka the stadium wave) currently has a period of c. 65 years, and the 20th century included two rising phases of the oscillation, explaining its two warming phases (1915-1945, and 1976-1997; Fig. 7.1).
Meridional transport was further reduced during the 20th century by the coincidence of the Modern Solar Maximum (Fig. 7.1): A long period of above average solar activity between 1935 and 2004. It is the longest such period in at least 600 years. Solar activity acts mainly on stratospheric energy transport, but since it affects the strength of the polar vortex and the El Niño/Southern Oscillation (see Part II), it also influences tropospheric transport.
In Fig. 7.1, the top panel shows solar activity. High solar activity weakens poleward energy transport causing warming. The bottom panel shows that the ascending half-period of the Atlantic Multidecadal Oscillation causes an even bigger reduction in energy transport and has a larger positive temperature effect. The middle panel is the temperature evolution for the past 120 years. It is consistent with the effect of these two factors on transport. The sunspot data is from SILSO, the temperature data shown is the HadCRUT4 deseasonalized temperature, and the AMO data, also deseasonalized, is from NOAA. It has been smoothed with a gaussian filter.
As can be seen in Fig. 7.1, most of the warming during the 20th century can be explained by the combined effect of the ocean multidecadal oscillations and the Modern Solar Maximum on meridional transport. No other proposed factor can satisfactorily explain the early 20th century warming period, the mid-20th century shallow cooling, and the late 20th century strong warming period, without resorting to ad-hoc explanations. In a single century two periods of reduced transport (warming), coincided with the ascent of the Atlantic Multidecadal Oscillation and the effect of the modern solar maximum. This resulted in 80 years of diminished transport that contributed to the greatest warming in 600 years, triggering political and scientific alarm.
7.3 Solar changes, transport changes, and climate shifts
The amount of energy transported poleward varies continuously, with major seasonal changes. However, at certain times the annual average atmospheric transport at high latitudes changes more rapidly over a period of a few years and settles into a different average strength. These abrupt changes in transport are mainly a winter phenomenon, and cause climate shifts on average every 25 years. Climate shifts were first identified in 1991 (Ebbesmeyer et al. 1991), yet they are not considered a cause for climate change in the IPCC reports, despite numerous studies suggesting they are. After each shift, the climate settles into a new regime.
It is known that one of these shifts took place in 1976 resulting in accelerated warming, and another one in 1997, resulting in decelerated warming (see Part IV). The four known shifts that took place in the 20th century happened soon after solar cycle minimums. The climate regimes, or meridional transport phases, disproportionally affect the Arctic climate in an opposite direction to the climate of the northern mid-latitudes. The accelerated warming from 1976-1997 was characterized by a quite stable Arctic climate, but the decelerated warming since 1997 has coincided with strong Arctic warming. Figure 7.2 shows how the sudden Arctic shift of 1997 was caused by an increase in meridional transport. The only energy that reaches the Arctic in winter is through transport, and the shift was accompanied by an abrupt increase in the amount of energy radiated to space.
According to IPCC theory, without a change in solar energy and/or a change in albedo (solar energy reflected by clouds and ice), a change in outgoing longwave energy could not happen, because energy out must match energy in. Yet without a significant change in either solar energy or albedo, a significant change in outgoing longwave energy occurred, as shown in Fig. 7.2.
Climate scientists contributing to the IPCC reports cannot blame the 1976 climate shift on changes in atmospheric greenhouse gases, so they suggested it was caused by a coincidental small reduction in anthropogenic sulfate aerosols. They set the sulphate cooling effect to a point that allowed increasing CO2 levels to overcome the previous cooling trend in 1976. As the 1997 shift cannot be explained in terms of anthropogenic factors, any data that shows that the shift occurred is ignored, and the focus is shifted to the increased Arctic warming.
Climate shifts undoubtedly represent changes in the meridional transport of energy. No theory can successfully explain climate change without accounting for abrupt or gradual changes in transport. The Winter Gatekeeper hypothesis has been developed to explain how climate has changed naturally for the past 50 million years and how it is changing now, integrating into a single interpretation tectonic, orbital, solar, oceanic, and atmospheric causes of climate change. It has tremendous explaining power, and many apparently unconnected phenomena can be linked through it. As an example, changes in wind speed and evaporation are discussed below. Many climate scientists will be able to reinterpret their results guided by this new energy transport view of climate change.
Particularly challenging was to find an explanation for all the previously unconnected evidence of a strong effect on climate from small changes in solar activity. This 220-year-old problem constituted the genesis of the hypothesis. The evidence that small changes in solar activity affect the meridional transport of energy is very solid. Two pieces of evidence are mentioned here.
The first is the repeated observation during the past six decades that changes in solar activity have affected the Earth’s speed of rotation (see Part II). This can only be accomplished by solar-induced changes to atmospheric angular momentum that affect the global atmospheric circulation. This is not a small feat for such small changes in incoming energy, and it derives from the dynamical changes caused by UV (ultraviolet radiation) absorption by ozone in the stratosphere.
The second piece of evidence is that Arctic temperatures display a negative correlation with solar activity. This is not a recent development, as shown in Fig. 5.5. This negative correlation was demonstrated for the past two millennia by Kobashi et al. in their 2015 article “Modern solar maximum forced late twentieth century Greenland cooling.” Part of their figure 3 is shown as Fig. 7.3.
In Fig. 7.3, panel (B) is the Greenland temperature anomaly combined with the average NH temperature from four Northern Hemisphere records. Periods of warm Greenland anomalies in Greenland are in red, periods of cold Greenland anomalies are in blue. Panel (C) shows two TSI reconstructions by Steinhilber et al., 2012 and Roth and Joos, 2013 in z score. The blue areas are the periods of stronger solar activity, and the red areas are periods of weaker solar activity. Generally, the colored areas in (C) correspond to those in (B) with possible multidecadal lags. Panel (E) is a decomposition of the Greenland temperatures into solar-induced changes (blue) and hemispheric influences (orange) with a regression constant (–31.2°C; dashed black line), constrained by the multiple linear regressions. The error bounds are 95% confidence intervals. The green shaded area is the period (the late 20th century) when the modern solar maximum had strong negative influence (red circle) on the Greenland temperature. Figure 7.3 is from Kobashi et al. 2015.
The most plausible explanation for Arctic temperature displaying a negative correlation to solar activity is that changes in the sun regulate meridional transport. An increase in solar activity reduces transport, cooling the Arctic, and a decrease in solar activity increases transport, warming the Arctic. The effect on the temperature in the mid-latitudes is the opposite.
More evidence is provided by the relationship between solar activity and the strength of the polar vortex (see Fig. 5.4). While this relationship provides an explanation for the Arctic temperature-solar correlation, the polar vortex data cannot be extended back in time as much as Greenland temperature data.
7.4 The explaining power of the Winter Gatekeeper hypothesis
Climate research has increased enormously over the past few decades, and frequently changes in climate phenomena are discovered. When these changes do not fit into the IPCC-sponsored CO2 hypothesis, and are not properly reproduced by models using greenhouse gas-related theory, they are considered climate oddities and ignored by the climate science community, who are focused almost exclusively on anthropogenic changes. There are many of these phenomena. We have already mentioned the expansion of the Hadley cells (see Fig. 4.5f). We mention another example here.
At the turn of the century, it was noticed that wind speed over land had been decreasing for over two decades. The phenomenon was termed “global terrestrial stilling” (McVicar & Roderick 2010). It was worrisome because power generation by wind turbines is related to the wind speed to the third power, so the 15% reduction in wind speed observed over the U.S. translated into an almost 40% reduction in available wind energy. The land wind stilling is puzzling as models do not show it. Moreover, it was accompanied by an increase in wind speed over the ocean, so the proposed explanation at the time was that land surface roughness increased due to increases in biomass and land-use changes (Vautard et al. 2010), in another example of an ad-hoc explanation.
Then, unexpectedly, the wind stilling trend started to reverse between 1997 and 2010, and since 2010 all land regions in the Northern Hemisphere are experiencing an increase in wind speed (Zeng et al. 2019). The explanation turned to internal decadal ocean–atmosphere oscillations, that seemed to correlate.
It is unknown to many people, but evaporation over the oceans depends a lot more on wind speed than it does on sea-surface temperature. It was demonstrated that global sea-surface evaporation has closely followed changes in wind speed (Yu 2007; Fig. 7.4).
Fig. 7.4 shows that at the 1976-97 period of low transport/high warming, global ocean wind speed (black continuous line) increased in parallel to ocean evaporation (blue dashed line), while land wind (red dotted) entered a period of stilling. At the 1997 climate shift the trends changed. The data for Fig. 7.4 is from Yu 2007 and Zeng et al. 2019. Europe has been chosen because it is downwind of the main transport route to the Arctic in the North Atlantic and responds earlier to its changes. Since 2010 the trend is shared by wind over all terrestrial Northern Hemisphere regions.
Lisan Yu shows that between the 1970s and the 1990s:
“… the enhancement of Evp [evaporation] occurred primarily over the hemispheric wintertime,” while “the westerlies associated with the [Aleutian and the Icelandic] low systems strengthened and expanded southward”
The Winter Gatekeeper hypothesis can explain this evidence, which, in turn, supports the hypothesis. The 1976 shift reduced meridional transport due to atmospheric circulation becoming more zonal, this increased wind speed and evaporation over the oceans while decreasing wind speed over land, because most meridional transport takes place over the ocean basins. The changes were more intense during the winter season, when more energy must be transported poleward, and resulted in a low-transport, high-warming, global climate regime (Fig. 7.1). At the 1997 shift the increase in meridional transport was caused by a more meridional atmospheric circulation, decreasing wind speed and evaporation over the oceans while increasing wind speed over land. The climate regime shifted into a high-transport, low-warming one.
It is obvious that changes in non-condensing greenhouse gases and anthropogenic aerosols could not have been the driving force behind these changes in meridional transport. This suggests they have been attributed too much climate sensitivity in climate change theory and models. However, the changes in transport and atmospheric circulation are clearly associated with changes in evaporation and air moisture that, without a doubt, must affect changes in cloud formation and transport, not forgetting changes in seawater salinity. Hypotheses that explain recent climate change in terms of water vapor and cloud changes might be subservient to the Winter Gatekeeper hypothesis. The integration of solar, astronomical, and atmospheric-ocean oscillation changes makes this hypothesis an all-encompassing one. It is more likely to be correct than partial hypotheses.
7.5 Some questions and comments about the hypothesis
Given the complexity of the climate system we do not have answers to every question, nor it is required that we do for the essence of the hypothesis to be correct. Some interesting comments came up in the discussions and it is worthwhile to bring them up, for those readers that missed them. Here we review a few of the more interesting questions and comments:
(1) Q: Is it necessary that there has been an increasing trend in solar activity since the Little Ice Age?
A: While an increasing trend in solar activity since 1700 is defensible, it is not required for the solar part of the hypothesis to be correct. As Fig. 7.1 shows, it is enough that an above average activity has reduced meridional transport contributing to the warming. The displayed Modern Solar Maximum had that effect. Fig. 7.3 provides strong support for the solar-transport link over the past two millennia.
(2) Q: Is the greenhouse effect required for the Winter Gatekeeper hypothesis?
A: Yes. In a thought experiment, it was proposed that a reader imagine that the polar regions are another planet (B) that is connected to a planet A made of the tropics and mid-latitudes. The connection allows the transfer of heat. The greenhouse effect in planet B is weaker since its atmosphere has a low water vapor content. During 6 months of a year planet B is in the dark. If more energy is allowed to pass to that planet, it is radiated more efficiently to space and the binary system average temperature decreases, despite planet B warming. The opposite happens if less energy is allowed to pass.
(3) Q: Why is there no correlation between surface temperature and solar activity if the hypothesis is true?
A: Because there shouldn’t be a correlation. At the multidecadal scale, meridional transport responds primarily to the multidecadal ocean-atmosphere oscillation. At the inter-annual scale, the Quasi-Biennial Oscillation and El Niño/Southern Oscillation have a strong effect. The Sun is not dominant at these time-scales. The role of the Sun increases as the time scale lengthens due to its longer-term secular cycles and their longer-term cumulative effect.
(4) Q: How important is the role of ocean transport in climate change in your hypothesis?
A: Oceans store most of the energy in the climate system, and most of the solar energy flows through the ocean before reaching the atmosphere. It therefore has a crucial role in climate. However, the role of the ocean in meridional transport is secondary to the role of the atmosphere and so is its role in climate change. Ocean transport is currently considered to be mechanically driven, with winds and tides providing the required energy. The atmosphere transforms heat into mechanical energy, while the ocean does not. This does not diminish the effect of the heat the ocean transports, which is about one third of total meridional heat transported. It also carries all the heat transferred from the Southern to the Northern Hemisphere. But the importance of ocean transport decreases with the increase in latitude, and so the Winter Gatekeeper hypothesis cannot rely on ocean transport except in a supporting role.
(5) Q: Do changes in solar activity affect ocean currents?
A: Changes in solar output should not affect ocean currents directly because that requires mechanical energy. Changes in solar output must necessarily affect the atmosphere first. This is important because it essentially rules out solar hypotheses that propose an initial solar effect over the ocean.
(6) Q: Does your hypothesis rule out warming from anthropogenic forcing like greenhouse gas emissions, industrial aerosols, and land use changes?
A: No. It just leaves a lot less room for them. If the hypothesis is correct, it is unlikely that the anthropogenic effect on climate can account for more than half of the observed warming, and probably much less.
(7) Q: What about Svensmark’s cosmic rays-cloud hypothesis?
A: We have not found any evidence for that hypothesis.
(8) Q: Isn’t the change in irradiance during the solar cycle too small to affect climate?
A: The change in irradiance with the solar cycle is only 0.1%, too small to change the system energy budget significantly and drive climate change. The ultraviolet radiation part 200-320nm of the spectrum is only 1% of total solar irradiance energy, and it varies by 1% with the solar cycle (10 times the variation in total energy). So, the ultraviolet radiation change responsible for the solar cycle effect on climate is only 0.01% of the total energy delivered by the Sun. The other 0.09% of the energy change is irrelevant in terms of climate change and has no detectable effect. The solar effect on climate is not about the amount of ultraviolet solar energy, but its dynamical effects in the Earth’s atmosphere. 99.99% of the energy responsible for the solar effect is already in the climate system. An increase in meridional transport reduces its transit time through the system, while a decrease in transport increases its residence time causing the temperature changes.
(9) Q: Your hypothesis cannot be correct because the top of the atmosphere should be in radiative equilibrium and return the same amount of energy it receives.
A: That statement is incorrect. The radiative flux at the top of the atmosphere is never in equilibrium and the planet is warming or cooling all the time at any time frame considered. Nobody has ever identified a period when the amount of energy entering the climate system was the same as the amount of energy exiting the climate system. The Earth has no way of returning the same amount of energy it receives. Many not well constrained feedback mechanisms are responsible for what thermal homeostasis the planet is capable of.
(10) Q: Stratospheric temperature also shows a shift in 1997 from a declining trend to a flat trend.
A: Yes, that is evidence of the 1997 climate shift and the ongoing pause despite the 2016 El Niño. The stratospheric temperature trend has the reverse profile to surface temperature trend. Models believe this is due to changes in stratospheric CO2 and ozone, but models and observations disagree significantly (Thompson et al. 2012). The stratosphere temperature trend is consistent with what is expected if the Winter Gatekeeper hypothesis is correct.
(11) Q: Scientists are already aware that changes in meridional transport are a possible cause for warming. See Herweijer et al. 2005.
A: The IPCC does not believe changes in transport have significantly contributed to the observed warming since 1951. If they did it would be included in the natural (internal) variability that they have assigned a net zero effect (see Fig. 5.1). Models do not reproduce transport correctly, and Herweijer et al. 2005 is an example. Models assume that the sum of ocean and atmospheric transport is nearly constant. This is called the Bjerknes compensation hypothesis (see Part IV). In their model experiment they increase ocean transport by 50% and observe warming from water vapor redistribution changes (greenhouse effect changes) and a reduction in low cloud albedo and sea-ice albedo. The problem is they fail to mention that their model-based proposed mechanism should work as negative feedback to warming. In a warming planet with polar amplification and a reducing latitudinal temperature gradient, a reduction in ocean transport is both implied and observed (they acknowledge it, referring to McPhaden & Zhang 2002). According to their model experiment this should drive cooling from transport changes, not warming. Their failure to mention this is misleading, to say the least. In a serious challenge to the model-based Bjerknes compensation hypothesis, researchers have found a strengthening of the North Atlantic Current since 1997 (Oziel et al. 2020) simultaneous with the strengthening of the atmospheric transport shown—and referenced in our articles—and in agreement with the Winter Gatekeeper hypothesis.
(12) Q: Shouldn’t the tropical convection zones be the main radiators of the planet, responsible for cooling? Directing heat away from the wet tropics should warm the planet.
A: That is incorrect. More energy is lost at the tropics than at the poles, but the energy loss at the tropics is essentially capped by deep convection. There is a point when additional downward energy does not increase surface temperature because it is used to increase convection. The proposal that deep convection acts as a thermostat in the tropics is over 20 years old (Sud et al. 1999). Deep convection transfers excess energy to the atmosphere but reduces outgoing longwave radiation through cloud formation. Most of the energy remains within the climate system. The negative correlation between sea surface temperature and outgoing longwave radiation, once temperature exceeds 27°C, is a well-known feature of tropical climate (Lau et al. 1997). The standard view is that transporting more energy toward the poles warms the planet. Our hypothesis and the evidence we have presented supports the opposite view.
(13) Q: The essence of Arctic amplification in winter is not what you say, but the impact of increasing sea temperatures, the decline in sea-ice and the increase in winter clouds, that are changing the Arctic to a warmer regime.
A: That is the position of most climate scientists. We disagree. That is the effect. The cause is a change in the amount of heat transported by the atmosphere to the Arctic that took place quite abruptly in a few years after the 1997 climate regime as shown in Fig. 7.2. This increase in heat and moisture transport produced the rapid decline in sea-ice and increase in cloudiness that are features of the new Arctic regime. All consensus Arctic predictions are failing because the situation stabilized in the new transport regime instead of causing positive feedback—the logical conclusion if the consensus position were correct.
(14) Q: Your view of El Niño/Southern Oscillation is incorrect. La Niña and El Niño are the alternating states of an oscillator.
A: That is not supported by a frequency analysis of the El Niño/Southern Oscillation. El Niño and La Niña are opposite deviations from the neutral state. Our analysis shows the frequency of La Niña years displays a strong negative correlation with the frequency of neutral years (see Fig. 2.4), not El Niño years. And the frequency of neutral years follows the solar cycle. There is only one way to interpret this evidence. La Niña and neutral are the alternating states of an oscillator that responds to solar activity. As neutral conditions are not opposite La Niña conditions, the oscillator tends to accumulate too much subsurface ocean heat. El Niño resets the oscillator. El Niño frequency depends upon how much extra heat the oscillator collects, which, in turn, depends upon whether the planet, overall, is warming or cooling. This is a very unorthodox view but it is supported by the evidence.
(15) Q: You show in Fig. 6.9 that over 85% of the surface warming shown in HadCRUT5 for the period 1997-2014 is the product of changes made to the temperature datasets since HadCRUT3. Is this correct?
A: Yes. Global annual average surface warming is not only a poor measure of climate change but, since it is calculated as an anomaly to an average, it is also a very small number relative to the accuracy of the measurements, and to the much larger seasonal temperature changes from which it is subtracted. The planet is warming but the numbers used to show it are not as meaningful as we are led to believe. A significant part of the warming claimed is due to the way it is calculated, as shown in the figure.
(16) Q: Do you really believe that you are correct and the IPCC is wrong?
A: Paraphrasing Einstein, if the IPCC is wrong it should not be necessary that one hundred authors show it. One is sufficient.
(17) Q: According to your theory, what should we expect from climate change in the next years and the rest of the century?
A: The current below average solar activity and an expected cooling phase in the Atlantic Multidecadal Oscillation indicate a probable continuation, or even accentuation, of the reduced rate of warming during the first third of the 21st century. A modest cooling during this period is possible. Unlike the 20th century, this century should contain two cooling phases of the Atlantic Multidecadal Oscillation. Even if another extended solar maximum takes place for most of the century, the 21st century should see significantly less warming than the previous one, regardless of CO2 emissions. A grand solar minimum is highly improbable according to our interpretation of solar cycles, which is a relief. Based on past evidence, a grand solar minimum sets the planet into a severe cooling trend.
(18) Q: What would be a good test of your hypothesis?
A: The expected climate change for the next 30 years, as described above is consistent with several alternative theories to the IPCC’s, based on the effect of the multidecadal oscillations. The Winter Gatekeeper explains better why the shift took place in 1997, and predicts the next shift for c. 2032, i.e., three solar cycles. The best test will be when a very active solar cycle takes place, if Arctic amplification turns into cooling and Arctic sea-ice grows it will support our hypothesis. If this happens, proposed alternatives to our hypothesis will be entertaining.