Abstract

John Wesley Powell, in the nineteenth century, introduced the notion that the 100th meridian divides the North American continent into arid western regions and humid eastern regions. This concept remains firmly fixed in the national imagination. It is reexamined in terms of climate, hydrology, vegetation, land use, settlement, and the agricultural economy. It is shown there is a stark east–west gradient in aridity roughly at the 100th meridian that is well expressed in hydroclimate, soil moisture, and “potential vegetation.” The gradient arises from atmospheric circulations and moisture transports. In winter, the arid regions west of the 100th meridian are shielded from Pacific storm-related precipitation and are too far west to benefit from Atlantic storms. In summer, the southerly flow on the western flank of the North Atlantic subtropical high has a westerly component over the western plains, bringing air from the interior southwest, but it also brings air from the Gulf of Mexico over the eastern plains, generating a west–east moisture transport and precipitation gradient. The aridity gradient is realized in soil moisture and a west-to-east transition from shortgrass to tallgrass prairie. The gradient is sharp in terms of greater fractional coverage of developed land east of the 100th meridian than to the west. Farms are fewer but larger west of the meridian, reflective of lower land productivity. Wheat and corn cultivation preferentially occur west and east of the 100th meridian, respectively. The 100th meridian is a very real arid–humid divide in the physical climate and landscape, and this has exerted a powerful influence on human settlement and agricultural development.

Abstract

The 100th meridian bisects the Great Plains of the United States and effectively divides the continent into more arid western and less arid eastern halves and is well expressed in terms of vegetation, land hydrology, crops, and the farm economy. Here, it is considered how this arid–humid divide will change in intensity and location during the current century under rising greenhouse gases. It is first shown that state-of-the-art climate models from phase 5 of the Coupled Model Intercomparison Project generally underestimate the degree of aridity of the United States and simulate an arid–humid divide that is too diffuse. These biases are traced to excessive precipitation and evapotranspiration and inadequate blocking of eastward moisture flux by the Pacific coastal ranges and Rockies. Bias-corrected future projections are developed that modify observationally based measures of aridity by the model-projected fractional changes in aridity. Aridity increases across the United States, and the aridity gradient weakens. The main contributor to the changes is rising potential evapotranspiration, while changes in precipitation working alone increase aridity across the southern and decrease across the northern United States. The “effective 100th meridian” moves to the east as the century progresses. In the current farm economy, farm size and percent of county under rangelands increase and percent of cropland under corn decreases as aridity increases. Statistical relations between these quantities and the bias-corrected aridity projections suggest that, all else being equal (which it will not be), adjustment to changing environmental conditions would cause farm size and rangeland area to increase across the plains and percent of cropland under corn to decrease in the northern plains as the century advances.

Studying rainfall and temperature data since 1980, Seager and his colleagues found this climatic boundary has already shifted east about 140 miles so that it now sits closer to the 98th meridian. And it will continue to move east as warming global temperatures increase evaporation from the soil and change precipitation patterns, they concluded.

According to a press release by Columbia University’s Earth Institute, “Seager predicts that as drying progresses, farms further and further east will have to consolidate and become larger in order to remain viable. Unless farmers turn to irrigation or otherwise adapt, they will have to turn from corn to wheat or some other more suitable crop. Large expanses of cropland may fail altogether, and have to be converted to western-style grazing range. Water supplies could become a problem for urban areas.”

Abstract
The Atlantic meridional overturning circulation (AMOC)—a system of ocean currents in the North Atlantic—has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature ‘fingerprint’—consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region—and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years.

These huge new wind turbines are a marvel. They’re also the future.
The latest model has blades longer than football fields. . . .

But especially in Europe, wind power is increasingly moving out to sea. And out in the ocean, with land barely in sight, the only limitation on size is engineering. Consequently, offshore turbines today are vaulting up even faster than onshore turbines have over the past decade.

A vivid example of this trend popped up in early March, when GE Renewable Energy announced that it will be investing $400 million to develop a new monster turbine: the Haliade-X, which will be (at least until the next big announcement) the biggest, tallest, and most powerful in the world. The first units are expected to ship in 2021.

It will be impressive as an engineering feat, but the significance of growing turbine size goes well beyond that. Bigger turbines harvest more energy, more steadily; the bigger they get, the less variable and more reliable they get, and the easier they are to integrate into the grid. Wind is already outcompeting other sources on wholesale energy markets. After a few more generations of growth, it won’t even be a contest anymore.

Meanwhile, the existence of Planet X, sometimes known as Nibiru, has been repeatedly debunked. Astronomers are searching for a possible Earth-size world in the outer solar system that they sometimes call "Planet X" or "Planet Nine," but this is not the same Planet X described by conspiracy theorists. In the conspiracy view, NASA is hiding the existence of a rogue planet that is hurtling toward Earth, ready to spark all manner of tsunamis and earthquakes as it zings by.

Nibiru originated from doomsday theorist Nancy Lieder. On her website, Lieder channels aliens called Zetas and peddles a complex web of interrelated conspiracy theories. Lieder first floated the idea of Nibiru in the 1990s and predicted its passage by Earth in 2003. Since then, the rogue planet has become the bogeyman of multiple doomsday predictions, including the 2012 Maya apocalypse, which was based on the supposed end of the ancient Maya calendar.