Satellite imagery

How Quickly Climate Change Is Accelerating, in 167 Maps

Posted by

0


WHEN IT COMES to explaining climate change, it helps to have clear, convincing evidence on hand. Ed Hawkins, a climate scientist at the University of Reading with a knack for data-visualization, specializes in precisely this kind of evidence.

Perhaps you’ve seen his work. His “Spiraling global temperatures” animation, which depicts a rainbow-colored record of global temperatures coiling outward at an accelerating pace, went viral back in May. It even made an (unexpected) appearance at the Olympic Opening Ceremonies in Rio.

His latest visualization, “Mapping global temperature changes,” is less abstract, but conveys a similar sense of urgency.

The infographic combines 167 global temperature maps—one for every year from 1850 to 2016—into a single chart. Those maps (Robinson1 projections, for those wondering) come from HadCRUT4, a gridded, color-coded dataset of global surface temperatures produced by the Met Office Hadley Centre for Climate Change. If you hover your cursor over the visualization at the top of this post, you’ll see that each map is divided into pixels colored varying shades of red and blue. Blue signifies cooler temperatures (relative to a 1961-1990 reference period) and red warmer ones. If a cell is grey, it indicates there was insufficient data to determine its color for that year.

ClimateChangeInline.jpg

The visualization couldn’t be more straightforward: As the years progress, the number and intensity of the red-colored cells increases. Slowly at first, then dramatically from around the 1980s onward. “It’s useful for presenting a simple message: the world is getting warmer,” Hawkins says.

The clarity of that message is a direct result of the way Hawkins presents the information. He uses the so-called “small multiples” technique, a method in which several images of identical scale and orientation are placed beside each other to encourage comparison not just between individual images, but the entire set. The fact that each map is further divided into pixels helps drive the message home. “That nearly every region has warmed links to people’s everyday experiences in their own location, and makes climate change more relevant on an individual level,” Hawkins says.

It’s a compelling way to visualize change over time—whether the data you’re perusing is a set of global heat maps, or satellite imagery of arctic sea ice.

NASA’s Tips For Interpreting Satellite Images.

Posted by

0


Example tip: Farmed vegetation often looks brighter green than natural vegetation

satellite image of the Okanogan-Wenatchee National Forest in Washington state

Straight Lines Mark Off Land Parcels in a Mixed-Use Forest.
NASA Earth Observatory image by Robert Simmon, using Landsat 8 data from the USGS Earth Explorer

Here at Popular Science, we love satellite images. They offer cool views of Earthly phenomena such as plankton blooms and erupting volcanoes. They give important perspective on the impact of natural disasters such as floods and fires. Seeing stuff from space can be a bit disorienting, however. But fear not. The Earth Observatory, NASA’s public site for its Earth sciences, has listed some cool patterns to look for while interpreting satellite images. Some highlights:

  • A line of clouds can indicate there are mountains below, as the mountains push warmer air upwards to higher elevations, where it cools and forms clouds. A line of vortices in the ocean, on the other hand, can indicate there are peaks below the surface of the water, perturbing the water’s flow.
  • There’s an optical illusion called relief inversion that can happen with satellite images. Mountains appear to be canyons, or vice versa. The Earth Observatory explains:

    It happens because most of us expect an image to be lit from the top left corner. When the sunlight comes from another angle (especially from the lower edge), the shadows fall in ways we don’t expect and our brains turn valleys into mountains to compensate. The problem is usually resolved by rotating the image so the light appears to come from the top of the image.

  • Farmed plants often look brighter green than natural vegetation.
  • Smoke often looks smoother than clouds. Haze is featureless and may be opaque if it’s dense, or translucent if it’s thinner. It’s not always possible to tell, just from visual inspection, the difference between white haze and natural fog.

Happy Earth-watching.

Satellite measures ‘quake island’.

Posted by

0


The “quake island” that rose from the sea off Pakistan this week is pictured clearly in a new satellite image.

It was acquired by the French Pleiades high-resolution Earth-observing system, and has enabled scientists to map the muddy mound’s precise dimensions.

_70161600_zalzalakoh

It is almost circular – 175.7m on the long axis and 160.0m on the short axis, giving a total area of 22,726 sq m.

The island, sited near the town of Gwadar, came up after the 7.7-magnitude tremor in the region.

Scientists say the intense shaking likely disturbed previously stable sediments and gas at the sea floor, which then oozed to the surface rather like a mud volcano.

The feature is not expected to persist. The ocean will erode the soft sediments, like it has with similar quake islands in the past.

The Gwadar mound is reported to be the fourth in the region since 1945, and the third during the last 15 years.

_70115209_89dfb451-8e71-4253-813f-8c7e3bc2242e

Pleiades is primarily a French national space project. It comprises two satellites that can resolve features on the ground as small as 50cm across.

The pair were built by Astrium, Europe’s largest space company; the imaging instrument was supplied by Thales Alenia Space (France).

Pleiades has both a civilian and a military role, and a number of European countries (Austria, Belgium, Spain and Sweden) have part-funded the project to get access to the pictures.