AIR
The atmosphere cycles energy, water, and carbon in a beautiful and delicate balance.
It swirls and changes in tandem with the oceans, maintaining a breathable atmosphere and a livable temperature. The Earth's gravitational pull prevents gases drifting off into space and forms a kind of planetary bubble. Life on Earth has evolved to thrive in the range of available temperatures, humidities, and climates, and the thick layer of gas shields us from harmful UV and solar radiation from space.
We think of air as simply the oxygen we breathe, but Earth's modern-day atmosphere is made up of many gases, and does a whole lot more for the life it supports.
The atmosphere is made up of 78% nitrogen, 21% oxygen, and other gases including carbon dioxide, argon, water vapour, neon, helium, and methane.
Between earth and earth's atmosphere, the amount of water remains constant; there is never a drop more, never a drop less. This is a story of circular infinity, of a planet birthing itself.
The seasons are an example of a cyclic pattern on Earth.
These regular changes in temperature and light are accompanied by patterns in weather as solar radiation heats up particles in the atmosphere and creates humidity, clouds, rain, snow, hail, and wind.
AIR TRAVEL
The 12km layer of gas that surrounds the Earth is thick with life.
Taking advantage of swirling air currents, organisms from viruses to plants to birds have found that air travel saves energy over long distances. It's a risky business, however. Far above the Earth's surface, the air is thin and cold, solar radiation is harsh, and navigation can be difficult without familiar landmarks like trees and rivers.
Barnacle Goose (Branta leucopsis)
Barnacle Geese spend the summer on Svalbard and Greenland, and migrate south to the UK and Netherlands in winter. There are four large flocks of barnacle geese, each with their own specific breeding and over-wintering locations that can shift with changing conditions. Each year, barnacle geese manage to find their way back to the same breeding and feeding grounds. Like other migratory birds, they achieve this feat of navigation by remembering landmarks, smells, positions of stars, and the Earth's magnetic field.
Great Snipe (Gallinago media)
These ultramarathon athletes can complete the journey from Sweden to central Africa, a distance of 6800km, in just 3.5 days. Great Snipes do not stop to eat or sleep but fly non-stop at a speed of almost 100 km per hour. Flying long distances is hard, hot work. Great Snipes travel around 2 km above sea level during cool nights but climb to a record-breaking 4.5 km above sea level during the day — perhaps to avoid overheating. By the time they reach central Africa, Great Snipes will have lost up to half of their body weight.
Swift (Apus apus)
Masters of life in the air, Swifts are able to predict the wind conditions along their migration route ahead. They time their journey to coincide with tail-winds which push them along, helping them to travel up to 830 km in a day. Swifts break their journey from Sweden to Africa into bite-size chunks. They choose their stop-offs carefully: only areas with plentiful insect food make the grade. Without the need for fatty energy reserves, they can start their migration slim, manoeuvrable, and able to evade predators.
Monarch butterflies (Danaus plexippus)
Some subspecies of Monarch butterflies take part in an epic relay played out over generations. Most Monarchs only live for four months. Nonetheless, swarms of butterflies migrate north in the spring, breeding as they go, to spend the summer in the USA and southern Canada. The northwards trip may take up to five generations of butterflies to complete. The south-bound autumn trip down to California and Mexico is much faster; completed by a single 'super generation' of large-bodied butterflies that live for up to eight months. Monarchs gather together in their hundreds to spend the winter hibernating in roosts.
Seeds and pollen
Before insects existed, plants harnessed the wind to distribute their pollen and seeds. Airborne pollen must be light and dry to stay aloft, and is produced in huge quantities as most is wasted. Now, about 12% of flowering plants are wind pollinated, including crop plants like wheat and rice.
Magnified pollen grain
Magnified pollen grain
Wind-pollinated plants don't need to attract insects. Instead, they catch pollen directly from the air using sticky structures. Seeds have to be relatively large to contain food for developing seedlings so wind-dispersed seeds have large wings, fluff, or feathery tails to be caught and carried by air currents. Another approach is to use wind action to catapult smaller seeds from hole-filled seed heads.
Magnified pollen grain
Magnified pollen grain
Air currents help life disperse around the globe, but the same currents can also bring unwanted pollutants.
In Spring 2010, the Icelandic volcano Eyafjallajokull erupted.
The eruption melted the volcano's overlying icecap and blasted over a quarter of a million cubic metres of molten rock into the atmosphere in the form of ash, cinders, and blocks.
Meltwater flowed down into the active crater where it rapidly cooled the magma below the surface.
The result was explosive.
Ash was blown into the atmosphere as a volcanic plume, filling the air, and blanketing the surrounding land.
This scoria, from a volcano near Eyafjallajokull, is an example of small chunks of lava blown from the crater in explosive eruptions.
This scoria, from a volcano near Eyafjallajokull, is an example of small chunks of lava blown from the crater in explosive eruptions.
Lava erupting from Eyafjallajokull melted the ice cap. Part of the meltwater then flowed down the side of the volcano and caused severe flooding in surrounding villages.
The cloud of abrasive ash was picked up by winds and blown across Northern Europe.
If abrasive volcanic ash gets into aircraft engines, it can damage surfaces and make flying dangerous. European air space was shut down completely as a safety precaution. Nearly half of global air traffic was halted during the eruption, affecting about 10 million passengers.
Air travel worldwide was brought to a halt for a week, holiday-makers were stranded, air freight was grounded, and economies stalled.
The map here shows the total extent of the ash cloud as it shifted position over a month before settling to the ground.
WHEN THE WIND CHANGES
Hot, cold, wet, dry, calm, stormy...
Weather is the temporary state of the atmosphere.
Weather systems are among the most important systems on Earth.
They facilitate processes such as continental weathering and the carbon cycle, and create the vast variety of environments which life has evolved to survive and thrive in.
Earth's wind and water move in tandem.
Where atmospheric currents flow, driven by energy from the sun, ocean waters are pushed across seas in a mirror image.
Equatorial air warmed by the sun rises and flows towards the poles, shedding heat and precipitation, and sinking as it does so.
The air returns from the poles across the ocean surface, bringing cool air to the tropics and creating more-or-less predictable wind currents like the trade winds.
The Pacific trade winds that blow east to west are subject to frequent natural disruptions referred to as El Niño and La Niña.
These deviations from the norm have far-reaching environmental and economic consequences across the planet.
El Niño and La Niña events are a natural part of the weather system but their effects can have catastrophic impacts on events already stressed by anthropogenic climate change.
The 2014-16 El Niño event was one of the strongest ever recorded.
Explore the map below to learn about the global impact of El Niño weather events:
La Niña events occur as the planet returns to normal after El Niño.
The 2010-12 La Niña event was one of the strongest ever recorded. La Niña events tend to cool the global climate and so can, just for a while, mitigate the effect of climate change on global temperature.
We are currently experiencing a rare 'triple-dip' La Niña event — three La Niña events in a row.
Explore the map below to learn about the global impact of La Niña weather events:
"East Africa is experiencing a prolonged drought. Consecutive dry seasons have resulted in failing crops, water stress, and migration. The primary cause is the El Niño Southern Oscillation (ENSO) being in a La Niña phase for many seasons.
A related oscillation is the Indian Ocean Dipole which can reduce rainfall in East Africa when the western ocean warms and the east cools. These oscillations can reinforce each other and cause extreme impacts in East Africa.
Our research examines how global climate variability translates to local weather patterns and extreme conditions and how well climate models simulate these physical processes.
While future climate projections are critical information for equitable adaptation, most models aren’t developed or evaluated with Africa in mind. Our research provides valuable information for improving modelling tools and local adaptation planning. "
– Ellen Dyer, Postdoctoral Researcher (University of Oxford)
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