The 1998-2012 “pause” was a result of a very strong El Nino in 1998 with moderately strong La Nina at the end of the period. El Nino with westerly winds dominant at low and mid latitudes pushes warm water from the West Pacific across the ocean, slowing ocean uptake of atmospheric warmth, La Nina has conditions with easterly winds dominant at those latitudes pushing cooler East Pacific surface water across the oceans surface, increasing ocean uptake of atmospheric warmth. The effect is easy to see when you look at what temperatures were doing in the Pacific compared to the rest of the world.

The relationship, if it exists, is not a strong influencer. The hypothesis is that the solar magnetic fields associated with sunspots tend to divert galactic rays away from the Earth. These rays are thought to be catalysts for cloud formation, so during decades-long durations of lower number of sunspots, the galactic rays are able to form slightly more clouds than during times with sunspots, and the Earth cools over the course of those decades. The hypothesis in not that the Earth’s temperature follows the sunspot curves, such as the ones shown above in Robert’s post, but acts slowly over decades or centuries. The observations from which this hypothesis is created are the Maunder Minimum and the Dalton Minimum. The first corresponds with the Little Ice Age, and the temperatures fell a little bit for the second. The Earth’s temperatures have been generally rising ever since, so global warming may be nothing more than a recovery from the Little Ice Age and not so much associated with man’s activities, such as the tremendous increase in fossil fuel use over the past century. To verify this hypothesis and come closer to making it a theory, it must successfully predict cooler temperatures during another long period of low sunspot activity. This could take a few centuries to happen, or it could conceivably by happening now.

We already know that the “pause” that started in the mid 1990s was either not associated with man’s activities, as we all were still emitting similar amounts of CO2, or else it was associated with the reduction of CO2 production from the United States, despite not signing the Kyoto Accords, so the U.S. reduction has saved us from global warming. Since no one cheered that we were saved but instead the climatologists declared that the cessation of global warming was merely a “pause,” then we can conclude that there are forces influencing Earth’s temperatures and climates that far exceed man’s contributions. Otherwise the temperature increase would not have paused, because we continue to emit CO2, worldwide, at an ever increasing rate, thanks to the Kyoto Accord and the Paris Agreement exclusions of China, India, Brazil, and other nations that continue to build many, many coal fired power plants and to burn down their rain forests.

Another hypothesis that I came across in the late 1980s associated global temperature changes with the periods of the solar maxima. I vaguely remember that higher temperatures corresponded to shorter periods. This hypothesis came with a chart showing the correlation, but I kept the chart folded in my wallet and it eroded away in about a decade.

Many non-solar hypotheses also exist. One of my favorites is that forested areas tend to have higher air temperatures because the vegetation releases water vapor, a major greenhouse gas. Since we now have more forested land in many parts of the world than we had a century ago, this hypothesis suggests that global temperatures should be increasing. However, Brazil is burning down its rain forest, so maybe global temperatures could begin to fall. Ha! Now that I think about it, maybe that is where the “pause” comes from: Brazil has finally burned more forest than has grown elsewhere. This hypothesis just moved up one notch closer to the solar cycle hypotheses on my favorites.