Seasonal Change

Early Autumn / Early Spring
Mississippi River, north
of Lock and Dam No. 1

Seasons are distinguished by changes in weather, ecology, and hours of daylight. What accounts for seasonal changes?

“One must maintain a little bit of summer, even in the middle of winter.” ― Henry David Thoreau

A common misconception is that seasons occur because of differences in the distance between the Earth and the Sun throughout the year.

Seasons are not caused by variations in distance between the Earth and the Sun. The variation is distance between the Earth and the Sun is relatively small.

The perihelion, when the Earth is closest to the sun (94,445,000 miles), occurs around January 4th (position 1, left).

The aphelion, when the Earth is furthest from the sun (94,555,000 miles), occurs around July 3rd (position 2, left).

A number of years ago, the documentary “A Private Universe,” about how we misperceive the world around us, was filmed at Harvard’s commencement. Twenty-three faculty members, alumni and graduating seniors were asked, “Why is it warm in the summer and cold in the winter?” All but two answered incorrectly, saying the Earth was closer to the sun in the summer than in the winter (it’s actually closer in January). ― John Edward Huth

Four Seasons

The four seasons of the year are caused by variations is sunlight due to the 23.5° tilt of Earth's axis.

When summer occurs in a hemisphere, it is receiving more direct sunlight than the opposite hemisphere where it is winter.

In winter, sunlight hits the earth at oblique angles so it is less concentrated.

Seasonal changes become more pronounced as our absolute latitude increases (i.e., as we move farther from the equator).

In the northern hemisphere, summer is warmer than winter because sunlight hits the Earth at a more direct angle. Summer days in the northern hemisphere are much longer than the nights.

Much of our literature has been written with a northern hemisphere bias:

“What good is the warmth of summer, without the cold of winter to give it sweetness.”
― John Steinbeck, Travels with Charley: In Search of America

The carousel-like change experienced traveling on what Buckminster Fuller popularized as Spaceship Earth, is captured in Joni Mitchell's song The Circle Game:

And the seasons they go 'round and 'round
And the painted ponies go up and down
We're captive on the carousel of time
We can't return we can only look behind
From where we came
And go round and round and round
In the circle game

REFERENCES

• Earth's Orbit, Wikipedia.
• Losing Our Way in the World, by John Edward Huth, New York Times, July 20, 2013.
• Season, Wikipedia.

A Changing Climate

Glacier Bay

Voltaire said, "Men argue, Nature acts."

Indeed the Earth is a planet of relentless action.

Science draws from an abundance of data to interpret Earth's changes.

The Paleoclimate Record

Paleoclimatologists consider data preserved within rocks, sediments, ice sheets, tree rings, corals, shells and micro-fossils when determining the past states of the Earth's climate and atmospheric system.

“The paleoclimate record shouts to us that, far from being self-stabilizing, the Earth's climate system is an ornery beast which overreacts even to small nudges.”
― Wallace Broecker

The Modern Record

The modern record of science (since the late 19th century) gives us a plenitude of atmospheric temperature data from weather stations distributed around the globe.

A NASA animation (below) uses near surface atmospheric temperatures between 1880 and 2011 to illustrate above average temperatures (shades of red) and below-average temperatures (shades of blue) over 131 years.

Clearly global temperatures have warmed significantly since 1880 and most notably since the 1980s. Many of us see and feel the effect. What is the cause?

Cause and Effect

Cause and effect is a fundamental principle of classical physics. The effect of temperature change is a matter of record. There are a wealth of globally distributed temperature measurements that render the effect indisputable. Temperatures are rising.

The cause of this temperature change has been controversial. However an overwhelming majority of the controversy has been stoked by science-averse, and fact-challenged, climate change deniers with a political ax to grind.

“Those who cannot change their minds cannot change anything.”
― George Bernard Shaw

The overwhelming majority of scientists attribute the steady temperature rise to the corresponding rise in greenhouse gas emissions from energy production, industry and motor vehicles.

The science and engineering challenge of this millennium is to address the symptoms of climate change, but more importantly, to understand, buffer, and counter-act the destabilizing impact of humanity.

“Go to heaven for the climate and hell for the company.”
― Mark Twain

REFERENCES

• Climate Change Denial, Wikipedia.
• Greenhouse Gas, Wikipedia.
• Paleoclimatology, Wikipedia.
• The Discovery of Global Warming- The Modern Temperature Trend, Spencer Weart, American Institute of Physics, February 2013.

The Biosphere - A Finite Life Raft

Biosphere was coined and defined by 19th century geologist Eduard Suess as:

"The place on Earth's surface where life dwells."

The biosphere interacts with the elements of the lithosphere, hydrosphere, and atmosphere.

Trees, plants, and grasses are rooted in the pedosphere which is the topmost layer of the lithosphere comprised of soil, water, air, and living organisms.

The silhouette of a tree against the sky is a fitting metaphor for the biosphere as an interdependent and inter-connected system. Our biosphere is a delicate balance of inter-connected dependencies.

Bare Oak Tree

"Trees are poems the earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness."
― Kahlil Gibran

The biosphere is a finite life raft.

An anthropocentric view is that conservation and ecological concerns are meant to serve human needs. A holistic, deep ecology view recognizes the inherent value of all living organisms regardless of their human utility.

REFERENCES

• Deep Ecology, Wikipedia.

Following the Midnight Sun

Snæfellsjökull, Iceland after midnight

A 24-hour sun is a characteristic of an Arctic or Antarctic summer.

Inhabited areas in the Arctic Circle experiencing this phenomenon are known as the Land of the Midnight Sun.

"Sight is a faculty; seeing, an art."
― George Perkins Marsh, 1801-1882

Following the Light

The Arctic Tern is a migratory bird who follows the light by making a 44,300 mile round trip each year to experience the Arctic and Antarctic summers.

Arctic Tern Breeding & Migration

• Breeding grounds (red),
• Wintering grounds (blue), and
• Migration routes (green).

"There is symbolic as well as actual beauty in the migration of the birds... There is something infinitely healing in the repeated refrains of nature -- the assurance that dawn comes after night, and spring after the winter..."
― Rachel Carson, 1907- 1964

Arctic Terns live up to 34 years. After 34 years the migratory air miles logged would be equivalent to three round trips to the Moon.

An Arctic Tern in attack mode
protecting her nest.

Some feisty Arctic Terns chased us back into our rental car when we tried to explore one of the black sand beaches on the Snæfellsnes Peninsula in West Iceland.

Several shrieking alarm calls, combined with near-vertical dive-bombing routes aimed at the tops of our heads, indicated our presence was not welcome in what was probably a nesting colony.


REFERENCES

• Pole to pole, the extraordinary migration of the Arctic tern, by Steve Connor, 12 January 2010.