Tag: global warming

Four Centuries of Spring Temperatures in Nepal

In the past two decades, much scientific research has been conducted to examine the uniqueness (or non-uniqueness) of Earth’s current climate in an effort to discern whether or not rising atmospheric CO2 concentrations are having any measurable impact. Recent work by Thapa et al. (2015) adds to the growing list of such studies with respect to temperature.

According to this team of Nepalese and Indian researchers, the number of meteorological stations in Nepal are few (particularly in the mountain regions) and sparsely distributed across the country, making it “difficult to estimate the rate and geographic extent of recent warming” and to place it within a broader historical context. Thus, in an attempt to address this significant data void, Thapa et al. set out “to further extend the existing climate records of the region.”

The fruits of their labors are shown in the figure below, which presents a nearly four-century-long (AD 1640-2012) reconstruction of spring (Mar-May) temperatures based on tree-ring width chronologies acquired in the far-western Nepalese Himalaya. This temperature reconstruction identifies several periods of warming and cooling relative to its long-term mean (1897-2012). Of particular interest are the red and blue lines shown on the figure, which demark the peak warmth experienced during the past century and the temperature anomaly expressing the current warmth, respectively. As indicated by the red line, the warmest interval of the 20th century is not unique, having been eclipsed four times previous (see the shaded red circles) in the 373-year record – once in the 17th century, twice in the 18th century and once in the nineteenth century. Furthermore, the blue line reveals that current temperatures are uncharacteristically cold. Only two times in the past century have temperatures been colder than they are now!

Figure 1. Reconstructed spring (March-May) temperature anomalies of the far western Nepal Himalaya, filtered using a smoothing spline with a 50 % frequency cut off of 10 years. The red line indicates the peak temperature anomaly of the past century, the blue line indicates the current temperature anomaly, the shaded red circles indicate periods in which temperatures were warmer than the peak warmth of the past century, and the shaded blue circles indicate periods during the past century that were colder than present. Adapted from Thapa et al. (2015).

Figure 1. Reconstructed spring (March-May) temperature anomalies of the far western Nepal Himalaya, filtered using a smoothing spline with a 50 % frequency cut off of 10 years. The red line indicates the peak temperature anomaly of the past century, the blue line indicates the current temperature anomaly, the shaded red circles indicate periods in which temperatures were warmer than the peak warmth of the past century, and the shaded blue circles indicate periods during the past century that were colder than present. Adapted from Thapa et al. (2015).

In light of the above facts, it is clear there is nothing unusual, unnatural or unprecedented about modern spring temperatures in the Nepalese Himalaya. If rising concentrations of atmospheric CO2 are having any impact at all, that impact is certainly not manifest in this record.

 

Reference

Thapa, U.K., Shah, S.K., Gaire, N.P. and Bhuju, D.R. 2015. Spring temperatures in the far-western Nepal Himalaya since AD 1640 reconstructed from Picea smithiana tree-ring widths. Climate Dynamics 45: 2069-2081.

 

The Current Climate of Extremes

What a day yesterday! First, our National Oceanic and Atmospheric Administration (NOAA) announced that 2015 was the warmest year in the thermometric, and then the Washington Post’s Jason Samenow published an op-ed titled “Global warming in 2015 made weather more extreme and it’s likely to get worse.”

Let’s put NOAA’s claim in perspective.  According to Samenow, 2015 just didn’t break the previous 2014 record, it “smashed” (by 0.16°C).  But 2015 is the height of a very large El Niño, a quasi-periodic warming of tropical Pacific waters that is known to kite global average surface temperature for a year or so. The last big one was in 1998.  It, too set the then-record for warmest surface temperature, and it was (0.12°C) above the previous year, which, like 2014, was the standing record at the time. 

So what happened in 2015 is what is supposed to happen when an El Niño is superimposed upon a warm period or at the end year of a modest warming trend.  If it wasn’t a record-smasher, there would have to be some extraneous reason why, such as a big volcano (which is why 1983 wasn’t more of a record-setter).

El Niño warms up surface temperatures, but the excess heat takes 3 to 6 months or so to diffuse into the middle troposphere, around 16,000 feet up.  Consequently it won’t fully appear in the satellite or weather balloon data, which record  temperatures in that layer, until this year.  So a peek at the satellite (and weather balloon data from the same layer) will show 1) just how much of 2015’s warmth is because of El Niño, and 2) just how bad the match is between what we’re observing and the temperatures predicted by the current (failing) family of global climate models.

On December 8, University of Alabama’s John Christy showed just that comparison to the Senate Subcommittee on Space, Science, and Competitiveness.  It included data through November, so it was a pretty valid record for 2015 (Figure 1).

Figure 1. Comparison of the temperatures in the middle troposphere as projected by the average of a collection of climate models (red) and several different observed datasets (blue and green). Note that these are not the surface temperatures, but five-year moving average of the temperatures in the lower atmopshere.

El Niño’s warmth occurs because it suppresses the massive upwelling of cold water that usually occurs along South America’s equatorial coast.  When it goes away, there’s a surfeit of cold water that comes to the surface, and global average temperatures drop.  1999’s surface temperature readings were 0.19°C below 1998’s.  In other words, the cooling, called La Niña, was larger than the El Niño warming the year before.  This is often the case.

So 2016’s surface temperatures are likely to be down quite a bit from 2015 if La Niña conditions occur for much of this year.  Current forecasts is that this may begin this summer, which would spread the La Niña cooling between 2016 and 2017.

The bottom line is this:  No El Niño, and the big spike of 2015 doesn’t happen.

Now on to Samenow. He’s a terrific weather forecaster, and he runs the Post’s very popular Capital Weather Gang web site.  He used to work for the EPA, where he was an author of the “Technical Support Document” for their infamous finding of “endangerment” from carbon dioxide, which is the only legal excuse President Obama has for his onslaught of expensive and climatically inconsequential restrictions of fossil fuel-based energy.  I’m sure he’s aware of a simple real-world test of the “weather more extreme” meme.  University of Colorado’s Roger Pielke, Jr. tweeted it out on January 20 (Figure 2), with the text “Unreported. Unspeakable. Uncomfortable. Unacceptable.  But there it is.”

 

Figure 2. Global weather-related disaster losses as a proportion of global GDP, 1990-2015.

It’s been a busy day on the incomplete-reporting-of-climate front, even as some computer models are painting an all-time record snowfall for Washington DC tomorrow.  Jason Samenow and the Capital Weather Gang aren’t forecasting nearly that amount because they believe the model predictions are too extreme.  The same logic ought to apply to the obviously “too-extreme” climate models as well, shouldn’t it?

The Buzz on Alex and Global Warming

Of course we’re referring to Hurricane Alex here, which blew up in far eastern Atlantic waters thought to be way too cold to spin up such a storm.  Textbook meteorology says hurricanes, which feed off the heat of the ocean, won’t form over waters cooler than about  80°F.  On the morning of January 14, Alex exploded over waters that were a chilly 68°.

Alex is (at least) the third hurricane observed in January, with others in 1938 and 1955.  The latter one, Hurricane Alice2, was actually alive on New Year’s Day.

The generation of Alex was very complex.  First, a garden-variety low pressure system formed over the Bahamas late last week and slowly drifted eastward.  It was derived from the complicated, but well-understood processes associated with the jet stream and a cold front, and that certainly had nothing to do with global warming.

The further south cold fronts go into the tropical Atlantic, the more likely that they will just dissipate, and that’s what happened last week, too.  Normally the associated low-pressure would also wash away.  But after it initially formed near the Bahamas  and drifted eastward, it was  in a region where sea-surface temperatures (SSTs) are running about 3°F above the long-term average consistent  with a warmer world. This may have been just enough to fuel the persistent remnant cluster of thunderstorms that meandered in the direction of Spain.

Over time, the National Hurricane Center named this collection “Alex” as a “subtropical” cyclone, which is what we call a tropical low pressure system that doesn’t have the characteristic warm core of a hurricane.

A 1,000-Year History of Eastern Australia Megadroughts: How Do They Compare with the Recent Occurrence of the “Big Dry”?

Drought is a common feature of climate; but every so often when a longer-lasting or somewhat severe drought occurs, it is not long before someone, somewhere, makes the claim that that drought was either caused or made worse by CO2-induced global warming. A simple test of this thesis can be conducted by examining the historic record of drought for the location in question. If it can be shown that similar (or greater) frequencies or magnitudes of drought have occurred in the past, prior to the modern increase in CO2, then it cannot be definitively concluded that the current drought is the product of anything other than natural climate variability.

Unfortunately, long-term historical drought records covering more than a few decades of time are lacking for most locations across the planet. As a result, scientists have sought to augment these short-term instrumental drought histories with much longer proxy records, records that will sometimes extend back in time several centuries to millennia. Such is the case in the recent study of Vance et al. (2015), who derived a 1,003-year proxy of historical drought in eastern Australia.

Two Millennia of Snowfall Accumulation in Antarctica

Providing the rationale for their work, Roberts et al. (2015) write that “the short and sparse instrumental record in the high latitudes of the Southern Hemisphere means investigating long-term precipitation variability in this region is difficult without access to appropriate proxy records.” It was therefore the objective of this team of nine researchers to extend the duration of the Law Dome, East Antarctica, snowfall accumulation record back in time an additional 750 years so that it would cover over two millennia.

The resultant 2035 year-long proxy (22 BC to 2012 AD) is presented in the figure below. As reported by the authors, the average long-term snow accumulation rate was calculated as 0.686 m yr-1 (27 inches) ice equivalent, which rate they say “is in agreement with previous estimates, and further supports the notion that there is no long-term trend in snow accumulation rates, or that any trend is constant and linear over the [2035-year] period of measurement.”

If this number seems low for such an icy continent, the fact is that most high-latitude locations in both hemispheres would qualify as deserts based upon annual precipitation. In many places, it is literally “too cold to snow” as the frigid air can hold only tiny amounts of moisture.

There were several decadal-scale oscillations in the record, described by the authors as “common,” with “74 events (33 positive and 41 negative) of at least a 10-year duration in the record.”  The three longest periods of above average integrated snowfall occurred over the intervals 380-442, 727-783, and 1970-2009, while the three longest periods of below average integrated snowfall occurred during 663-704, 933-975, and 1429-1468.

On the Bright Side: Tropical Cyclones in the Bay of Bengal During Warmer and Colder Phases of ENSO and the PDO

While the hypothesis that tropical cyclones will become both more frequent and more intense as planetary temperatures rise has long been debated, real-world evidence has consistently refuted it (see, for example, the many reviews of this subject posted under the heading of Hurricanes at the CO2 Science website). The latest example is the work of Girishkumar et al. (2015), who examined over five decades of tropical cyclone (TC) data from the Bay of Bengal (BoB) in the Indian Ocean. Specifically, the authors “investigated how the relationship between ENSO and TCs activity in the BoB during October–December varies on decadal time scale with respect to PDO.”

China Recycles: Another Attempt at Cap and Trade

China’s announcement of the implementation of a cap and trade system is not the first we’ve heard of their efforts to combat their rising carbon emissions. In November, China and the United States hyped an agreement in which China “intends” to curb emissions “around” 2030. Reproduced below is an article on that “agreement,” which will certainly be greatly referenced over the course of Xi Jinping’s visit.

For today’s announcement, as with all international pronouncements on climate change, we must wait until we see the fine print. The road to global warming has traditionally been paved with good intentions.