Cumberland Times-News


March 22, 2014

Earth’s climate keeps changing, but why?

Earth’s climate has been subject to change, long before humans walked the Earth. Why should the climate change?

The Earth is a dynamic planet, subject to the shifting of the crustal plates (which can lead to increased volcanic eruptions), the advance and retreat of glaciers and changes in the Earth’s motion about the sun (Earth’s axial tilt and the varying ovalness of the Earth’s orbit).

On our neighbor planets, Venus and Mars there is little or no climate change.

Venus’ surface conditions are dominated by its heavy heat trapping atmosphere which elevate its surface temperature to about 870 degrees F, day and night.

Direct sunlight never reaches Venus surface owing to the planet’s thick sulfurous clouds, averaging 10 times higher than our clouds. Venus has no seasons, as its poles are vertical to the plane of its nearly circular orbit.

Mars has seasons due to its oval shaped orbit and tilt of its axis. But even when Mars is closest to the sun, noon ground temperatures barely reach above freezing; but through the night, the daytime heat leaks into space, bringing the surface temperature before dawn to -100 F.

Mars is half as big as the Earth so most of its internal heat has leaked away. There were volcanoes in Mars’ distant past, emitting enough steam to form oceans and lakes.

But Mars’ low gravity has permitted most of its atmosphere to leak into space. The low Martian air pressure (about 1 percent of Earth’s) causes water to boil away. (The hydrogen gas in the early Earth’s atmosphere has similarly escaped.)

Through scientific analysis of ice cores and sediment cores from the ocean floor, we have an approximate record of the Earth’s climate over the past billion years.

We are now in a warmer interglacial period, emerging from a time when glaciers covered St. Louis about 15,000 years ago. But during this warming, our global temperatures have fluctuated. From AD 200 to 600, the average global temperature was 1 degree F warmer than today.

The Dark Ages (600 to 900 AD) had temperatures 2 degrees F colder than today. The Medieval Warm Period was 1 degree F warmer than today. During the Little Ice Age (1300 to 1850) the temperatures were 2 to 3 degrees F colder than today. (Currently, our average surface temperature is 59 degrees F.)    

Extensive glacier coverage such as the recent episode that Earth just emerged from are rather rare in the Earth’s past billion years. The three others were: Southern Hemisphere (260 to 340 million years ago), North Africa (450 million years ago) and the most severe (550 to 850 million years ago) when most of the Earth’s surface was frozen (called Snowball Earth).

The locations of the second and third glacial coverage may seem strange, but crustal plate motion had moved these areas near the poles at the time when they were covered by glaciers.

During the interglacial periods, the concentration of carbon dioxide in the atmosphere rose with the average global temperature. As the global temperatures dropped, the ocean could absorb more carbon dioxide and its concentration in the atmosphere fell as well.

What about today, when humanity is burning fossil fuels and driving our atmosphere’s carbon dioxide concentration to levels not seen in hundreds of thousands of years?

Past measurements of both the average global temperatures and the carbon dioxide levels show a good correlation between the two numbers.

Since the interglacial warming began, sea level has risen about 400 feet, owing to the melting of glaciers, whose waters flowed into the rivers and then into the sea.

More than half of the 300 largest port cities in the ancient world, built from 3000 BC to the fall of the Roman Empire are now submerged. It is clear that climate change occurred long before human history.

Now what part of the current change in climate is due to humans? What can be done to arrest any further warming? When the Earth warmed in the distant past, some animals were able to migrate northward and continue their way of life.

But if the temperatures rise markedly in the midwest U.S., it will be hard to move farms 300 miles northward.

Humanity is in for some hard adjustments. The people who will suffer the most include some Pacific Islanders (likely to be submerged), southern Bangladesh and southern China where about 200 million people will no longer be able to farm (as their ground water will be contaminated as the ocean encroaches).

Reference: Chapter 13 of “Earth: A Tenant’s Guide” by Frank Rhodes, a Ph.D. geologist and former President of Cornell.

SKY SIGHTS AHEAD: The moon is now seen only in the a.m. sky. On March 27 the brilliant planet Venus will appear just to the right of the lower tip of the crescent moon in the 6:30 a.m. eastern dawn.

Bob Doyle invites any readers comments and questions. E-mail him at . He is available as a speaker on his column topics.

Text Only
  • Peanuts and Cracker Jack beat any foam finger

    Times have changed, and for the better, as this week marks the third year in a row NFL training camps have opened and have not taken center stage in the cities of Baltimore, Pittsburgh and Washington. That, of course, is due to the play of the three baseball teams that inhabit said cities, the Orioles, the Pirates and the Nationals — two of whom hold first place in their respective divisions, with the other one entering play on Wednesday just 2 1/2 games out of first.

    July 23, 2014

  • Big loophole Big loophole

    How ironic — and how sad — that the Potomac Highlands Airport Authority plans a closed executive session to discuss the open meetings law.

    July 23, 2014 1 Photo

  • Don’t do it. Don’t do it

    Temperatures have been moderate recently but are projected to rise to the upper 80s and low 90s later this week, so we want to remind you: Never leave children unattended in a vehicle.

    July 21, 2014 1 Photo

  • He means well, and this time they spared his life

    Our pal Phil is the only re-enactor certified in writing by both the Lee and Custis families to portray Confederate Gen. Robert E. Lee (whose wife was Mary Anna Custis Lee). When he’s in uniform, he generally stops at the bottom of the path that leads to the summit of Little Round Top, salutes Capt. Gary and First Sgt. Goldy and asks permission to join us. (Get it? Generally ... General Lee?) We always return his salute and grant him permission, in part because he’s our friend and also because the real Lee never got to see what it really looks like from up there. (Get it? Grant ... Grant? U.S. Grant? Real Lee ... really? OK. I hear you. That’s enough. Seriouslee.) Phil gets a kick out of being able to sneak up on us while we’re distracted by tourists.

    July 20, 2014

  • It’s hotter here than in D.C. or Baltimore

    At this time of the year, the weather is a frequent subject of conversation, particularly the temperatures. We are now in the “Dog Days,” usually the hottest days of the year. The term comes from our sun appearing to be near the “Dog Star” (Sirius) and the “Little Dog Star” (Procyon). In reality, the sun is now about 94.5 million miles away while Sirius is 8.6 light years away with Procyon at 11 light years distance. Sunlight takes only 507 seconds to reach us, while the two dog stars’ light takes about a decade to travel to our eyes. So our sun is in the same direction (but not distance) as these two bright winter evening stars.

    July 20, 2014

  • Mike Sawyers and his father, Frank Sale of quart-sized Mason jars lagging, merchants claim

    The opening day of Maryland’s squirrel hunting season is Sept. 6 and I am guessing you will be able to drive a lot of miles on the Green Ridge State Forest and see very few vehicles belonging to hunters of the bushytail. It wasn’t always that way. In the early 1960s, when I was a high school student in Cumberland, there was no Interstate 68. What existed was U.S. Route 40 and in the last couple of hours before daylight on the opening day of squirrel season there was an almost unbroken line of tail lights and brake lights between Cumberland and Polish Mountain.

    July 20, 2014 1 Photo

  • Hugo Perez Columnist, son are range finders, but where are .22 shells?

    We feel pretty lucky on this side of the Potomac to have a nice shooting range to utilize for free and within decent driving distance.

    July 20, 2014 1 Photo

  • Opposition and inclusion understood

    Those of you who have been here before know how I feel about the late great Len Bias, who I will remember foremost as Leonard Bias, the polite, spindly Bambi-eyed kid from Hyattsville’s Northwestern High School, who could throw a dunk through the floor, yet had the most beautiful jump shot I have ever seen.

    July 17, 2014

  • Stopgap

    Kicking the can down the road was one of the things American kids did to pass the time in the old days, particularly if they lived in rural areas where there was little traffic to contend with.

    July 16, 2014

  • Further proof you should never bet on baseball

    Had you known in March that ...

    July 16, 2014