The Tide Is Turning, Time For Global Cooling
Climate scientists have constructed models to predict what Earth's climate will look like decades, even hundreds of years in the future. Unfortunately, many major components of Earth's climate system have not been accurately monitored for very long. This makes such predictions suspect if not laughable. A case in point are variations in ocean circulation and temperature. In the Atlantic there is a cycle for sea surface temperatures variation called the Atlantic Multidecadal Oscillation (AMO). The AMO is linked with decadal scale climate fluctuations like European summer precipitation, rainfall in Europe and India, Atlantic hurricanes and variations in global temperatures. A new study in the journal Nature reports that the AMO is again transitioning to a negative phase, meaning the vaunted “pause” in global warming may be with us for decades. In fact, scientists at the University of Southampton predict that cooling in the Atlantic Ocean could cool global temperatures a half a degree Celsius.
Climate scientists and oceanographers have studied ocean circulation patterns for years and—given the ocean's massive capacity for absorbing, storing, and releasing heat energy—they have long suspected linkage between sea surface temperatures (SST) and climate variation. Now that linkage is the subject of a new study titled “Ocean impact on decadal Atlantic climate variability revealed by sea-level observations.” In it, researchers from University of Southampton, led by Gerard D. McCarthy, have tried a new approach using sea level along the east coast of the US to estimate ocean circulation on decadal timescales. Here is the overview from the article's abstract:
Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres—the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO.
There are a number of cycles in Earth's short term, decadal scale, climate variability—the Pacific Decadal Oscillation (PDO), the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), and so forth. When it comes to the AMO the authors claim that circulation records do not go back far enough to get a really good handle on its behavior. This is despite the fact that NOAA publishes time series data going back to 1856. The researchers state their case this way.
The difficulty in linking ocean circulation changes to decadal climate variations lies in the fact that long observational records of ocean transports are rare. Measurements such as those of the Florida Current since 1982 and the Greenland–Scotland ridge transports since the mid-1990s are some of the longest continuous ocean transport records available. Continuous, full-depth, basin-wide measurements of the Atlantic overturning circulation only began in 2004 with the RAPID monitoring project at 26° N (ref. 13). None of these records are long enough to directly link ocean circulation with decadal climate variations such as the AMO.
The authors' claim that sea-level measurements from tide gauges provide an integrated measure of water column properties, offering time series of sufficient duration to study decadal ocean circulation variation. While using tide gauges to investigate ocean circulation is not new—an attempt to estimate Gulf Stream flow using tide gauges was made by R. B. Montgomery in 1938—this is the first time the technique has been applied to the AMO.
“The principle is based on geostrophic dynamics: on timescales longer than a few days, ocean circulation is in geostrophic balance so, looking downstream, the sea level is seen to increase from left to right in the Northern Hemisphere,” the paper explains. Historical data regarding sea-level change were gathered from Florida to Boston, as depicted in the figure below.
The study’s authors based their results on ocean sensor arrays and 100 years of sea-level data. After much crunching of numbers they decided that the picture is clear: in recent years, the sea-level index indicates that the AMO is shifting to a negative phase, consistent with observations of reduced overturning circulation.
“The observations of [AMO] from [sensor arrays], over the past ten years, show that it is declining,” Dr. David Smeed, a co-author, said in a statement. “As a result, we expect the AMO is moving to a negative phase, which will result in cooler surface waters. This is consistent with observations of temperature in the North Atlantic.” The relationship of the Sea-level circulation index, the NAO and the AMO are shown in the graph below.
The figure, taken from the paper, shows the accumulated sea-level index (blue), which is representative of subpolar heat content evolution, the accumulated NAO (red, dashed) and the AMO (black). The heat content proxy and the accumulated NAO have been normalized. All time series have been 7-year low-pass filtered. The accumulated sea-level index and accumulated NAO have been detrended.
The bottom line? The AMO is heading down and this means a cooling phase lies ahead. Such a cooling phase in the Atlantic will influence “temperature, rainfall, drought and even the frequency of hurricanes in many regions of the world,” says Dr. Gerard McCarthy. This could mean global cooling ahead, much to the consternation of climate alarmists everywhere. After all, it's hard to sell global warming when things are getting colder.
Indeed, this result is consistent with data from other areas, leading some scientists to argue that the world is headed for a cooling phase. Scientists from around the world have concluded that weakening solar activity could bring about another “Little Ice Age.” This is not a new idea but it has been drowned out by the clamor of the “CO2 is the climate control knob” crowd. As B. van Geel et al. wrote in Quaternary Science Reviews in 1999:
Evidence for millennial-scale climate changes during the last 60,000 years has been found in Greenland ice cores and North Atlantic ocean cores. Until now, the cause of these climate changes remained a matter of debate. We argue that variations in solar activity may have played a significant role in forcing these climate changes. We review the coincidence of variations in cosmogenic isotopes (14C and 10Be) with climate changes during the Holocene and the upper part of the last Glacial, and present two possible mechanisms (involving the role of solar UV variations and solar wind/cosmic rays) that may explain how small variations in solar activity are amplified to cause significant climate changes. Accepting the idea of solar forcing of Holocene and Glacial climatic shifts has major implications for our view of present and future climate. It implies that the climate system is far more sensitive to small variations in solar activity than generally believed.
The old climate change dogma was that solar irradiance only varied by a miniscule amount, roughly 0.1% as measured over the normal 11 year solar cycle. This has caused many scientists to dismiss changes in the Sun's output as unimportant to climate change here on Earth. But new research is proving this assumption to be shaky at best. In a long online post by NASA in 2013, a good overview of current research into the solar-climate link is presented.
As the online report states: “Of particular importance is the sun's extreme ultraviolet (EUV) radiation, which peaks during the years around solar maximum. Within the relatively narrow band of EUV wavelengths, the sun’s output varies not by a minuscule 0.1%, but by whopping factors of 10 or more. This can strongly affect the chemistry and thermal structure of the upper atmosphere.”
The full report, “The Effects of Solar Variability on Earth’s Climate,” is available from the National Academies Press. This research and more are causing the tide to turn with regard to climate change and the importance of our local star.
“The stagnation of temperature since 1998 was caused by decreasing solar activity since 1998,” said Jürgen Lange Heine, a physicist with the German-based European Institute for Climate and Energy (EIKE). “From 1900 to 1998, solar radiation increased by 1.3 W/m2, but since 1998 it has diminished, and could reach values similar to those of the early 20th century. A drop in global temperature over the next few years is predicted.”
It is amazing that climate scientists seem to have forgotten where the energy that drives Earth's climate comes from in the first place. The fact that McCarthy et al. have detected a trend in the AMO that indicates a future cooling trend only reinforces what solar scientists have been saying for several years. This is because the shift in the AMO is a result of the climate system changing, not a fundamental cause of climate change. It is a cyclic oscillation in a complex system driven by solar energy.
Of course, if the climate does start cooling, old guard global warming fanatics will be at pains to explain what is happening. The last thing they want is to change the focus of the climate change scare from human generated CO2. Science is self correcting when done correctly, but scientists are only human. They really hate to change their minds once they've settled on an explanation for something, even when that explanation grows less believable every day. As always, time will tell, because nature pays no attention to nattering hoards of foolish human scientists. I hope everyone is ready for a little global cooling.
Be safe, enjoy the interglacial and stay skeptical.