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In 2016 I was asked to give a PowerPoint presentation to a large hiking organization in SW Colorado covering the topic of “Changes in Atmospheric Composition and Temperature and Their Effects on Weather and Hiking”. It was well received, and as there are still a lot of people who don’t really understand all the interactions and causes, I thought it might be worthwhile to post a condensation of it as an article on this forum.
To begin with, I must say up front that I am a scientist / educator and am convinced by the data that these changes are taking place. According to the recent national election, there must be a bit less than half of Americans who may not agree with the data and my conclusions. Only in America do many people accept weather predictions from a rodent but deny climate change evidence from scientists. For those people, Happy Groundhog Day! And, if you are in that category, feel free to save your time, and stop reading this article now.
I gathered my information from scientific articles, the National Weather Service, NOAA, Weather Underground, National Climatic Data Center, National Geographic Society, insurance company data, numerous web sites, and personal observation.
In a nutshell, we are seeing an increase in weather extremes, and will continue to see more increases in the future…… more rain, more hail, more snow, more flooding, more flash floods, more drought, more wind, more lightning, more heat waves, more cold waves, more pest infestations, more wildfires, etc, etc. Yes, we will continue to have lots of nice days for hiking and climbing, but fewer overall every year as the years pass.
First, some specifics:
1. AIR TEMPERATURE The global air temperature at the Earth’s surface has increased 0.9 degree Fahrenheit between 1970 and 2010, and has risen more since. And, there is a far greater warming north of the Arctic Circle than below it.
2. HEAT WAVES – of which night time lows are one indicator – are striking a growing portion of the U.S.– a 31% increase, from 4% in 1970 to 35% in 2010.
3. MOISTURE has risen about 4% since 1970 according to satellite data. Average global specific humidity has gone from 10.2 in 1970 to 10.6 in 2010.
4. EXTREME RAINFALLS The percentage of the U.S. getting an elevated portion of precipitation from extreme events has risen from 9% in 1970 to 16% in 2010, and is increasing.
Everyone has probably heard of the warming effects of “greenhouse gases”, particularly CO2. Those effects are real, and CO2 is a major culprit (about 57%). However,there are also other contributors.
WHAT CAUSES GLOBAL WARMING ON EARTH
1. Greenhouse gases
A. H2O vapor – most abundant Greenhouse Gas – warms the Earth by reflecting heat back to Earth at night, cools by clouds reflecting sun light back into space during day time.
B. Carbon Dioxide (CO2) – large amounts created by combustion of hydrocarbon fuels (causes about 57% of global warming by gases)
C. CFC’s – 100% human created material, very powerful (15,000 X more effect per molecule than CO2) (25%)
D. Methane (CH4) about half is created by rice farming and cattle for human consumption (25X more than CO2)(12%)
E. Nitrous Oxide (N2O) about half caused by high temperature burning of hydrocarbon fuels (in coal and gas fired power plants, in jet aircraft, and in automobile engines) (230XCO2)(6%)
2. Plant removal
A. Some of the light energy that impacts plants is converted by plants, through photosynthesis, into chemical energy (sugars, starches, and oils). This conversion results in less energy being available to be converted in to heat energy, which can be radiated back into the atmosphere. Thus a cooling effect. However, deforestation, urbanization, and other plant removal schemes remove these organisms that were creating the energy reducing / cooling effect.
B. As photosynthesis takes place, green plants remove CO2 from the air and produce oxygen. When the plants are removed, or burn, or die, this CO2 removal function is lost.
3. When plants or any carbon-based fuels (coal, oil, natural gas, wood, etc) are burned massive amounts of CO2 are produced. Because of this, CO2 is being produced about 400,000 times faster than it is currently being sequestered by plants.
4. Albedo – light absorption - land surface changes – heat conversion vs. light reflection. Anything with a dark color will absorb light and convert it to heat. Conversely, the lighter the color, the more light energy will be reflected back into the atmosphere. For example – put your hand on a white car in the summer and then on a black car- note the temperature difference.
A. A black roof or black road (such as asphalt) will absorb light energy and get hot during the day (low albedo)
B. A white roof or road (such as concrete) will reflect more energy and notget as hot during the day (high albedo)
C. When land surfaces are changed by development of any kind, the albedo is usually changed
5. Urban Heat domes – buildings and pavement absorb heat all day, and radiate it into air at night. Buildings have more surface area than the land they are built on. This increased surface area (the walls of the buildings) absorbs heat during the day, and radiates it back into the air at night. Compounding the situation, as noted above, if the buildings and / or pavement are dark in color in areas that are exposed to direct sunlight, more heat will created. This combined effect makes for a more intense heat dome. Going a step farther, if the urban area has a traditional wind pattern at night, as most areas tend to, the air warmed by the buildings will rise, thus forcing the winds to flow over, or around, the area, thus reducing the cleansing / mixing effect of evening winds, and the area experiencing the urban heat dome will also experience more air pollution. Increased air pollution will reflect more heat back to the ground… quite the compounding effect…. A “local” warming. As the human population migrates to cities, and they get larger, more and more urban heat domes are created.
6. Limestone is being converted to Portland cement in huge volumes for construction, and in the conversion process large volumes of CO2 are created and released into the atmosphere. Limestone (CaCO3) is heated → CaO (Portland cement) + CO2. Living organisms in the sea sequester CO2 in the production of shells, which eventually form the rock limestone. Limestone is a huge CO2 reservoir for the Earth.
7. As noted above, most limestone is created by living organisms over time, combining CO2 dissolved in water with Calcium. Chemical pollution and water temperature changes are severely reducing the numbers of these organisms today, reducing the natural cycling of CO2, hence increasing amounts of CO2 in the atmosphere and waters.
There is a greater warming north of the Arctic Circle which is being mostly caused by the deposition of black soot resulting from hydrocarbon burning (diesel, coal burning, wildfires, dung burning, etc), in mid-lattitude areas that are carried northward by atmospheric processes. Soot heats the air 1 million times (1,000,000X) more per unit mass than does CO2, having a particularly strong warming effect over the Arctic. For example, January 19, 2016 the temperature at the North Pole was about 25 degrees F warmer than normal (the 100+ year average) for that date.
Weather patterns are often closely related to what is happening to the jet stream. A jet stream forms high in the upper troposphere between two air masses of very different temperature. The greater the temperature difference between the air masses, the faster the wind blows in the jet stream. The strongest jet stream winds occur between air masses having the largest temperature differences over the deepest layer of the troposphere. Since colder air is more dense than warmer air, there is an air pressure difference between them at any altitude. And if the warm and cold air masses are quite deep, higher altitudes in the atmosphere experience progressively larger air pressure differences. Even though the wind "tries" to flow from high pressure to low pressure, the turning of the Earth causes the air flow to turn to the right in the Northern Hemisphere (west to east), so the jet stream flows around the air masses, rather than directly from one to the other.
|Jet Stream Formation Profiles|
The jet stream tends to slow down due to the now warmer temperatures north of the Arctic Circle, and as it does, instead of the more normal fairly smooth west to east pattern (positive phase), it tends to take a more wavy west to east pattern (negative phase), with huge bends, creating high-amplitude troughs and ridges bulging northerly and southerly.
Slower progression of upper-level waves cause associated weather patterns in mid-latitudes to be more persistent, which lead to an increased probability of extreme weather events that result from prolonged conditions, such as drought, flooding, cold spells, and heat waves. Often, these huge bends will get stuck, and will not move, setting up “blocking highs” and “cutoff lows”, which result in extreme weather events that can last for days or weeks. Thus, we often see at the same time nasty cold and snow in the east and northeast U.S. (or heavy rains) and very warm and dry weather in the west and southwest U.S. (South-bending trough in the east and north-bending ridge in the west). And, sometimes just the opposite, depending on where the wavy pattern happens to get stuck.
Heavy precipitation days are increasing even in places where precipitation is decreasing, such as the 2015 devastating flash floods in Death Valley, California. “Dirty air” (pollution) fosters precipitation extremes. Changes to clouds suppress precipitation and encourage drought in some areas where moisture in low-lying clouds is in tiny droplets. And, in taller clouds pollution has the opposite effect – increasing heavy rain, hail, and wind. Very dirty conditions can increase the probability of heavy rain 50% and at the same time reduce the probability of light rain by 50%.
Certain common bacteria (Pseudomonas syringae, found on many plants) are sucked up into the air by fast rising air and facilitate the formation of more and larger hail. From 2010 to 2012 insurance claims resulting from hail damage increased 84%. Getting caught in a hail storm, especially with big hail stones, is no fun for hikers or climbers!
Now for some basic atmospheric physics: Warmer air can hold more water than cooler air. For example: One cubic yard of air can hold 1 teaspoon of water at 50 degrees F, 2 teaspoons of water at 73 degrees F, 3 teaspoons of water at 85 degrees F, and 4 teaspoons of water at 93 degrees. Heat energy is required to cause water to evaporate. This energy is stored in that evaporated water, and is known as the “latent heat of water.” As water vapor condenses into liquid water this heat is given off into the air, which drives storms. Warm air rises, which causes updrafts. Common cumulus clouds have updraft speeds of about 5 mph. Typical thunderstorms have updraft speeds of 15-30 mph. And, today’s supercell thunderstorms, which are getting more common, can have updraft speeds of up to 175 mph. What goes up also comes down, and we are often seeing wind gusts going down at over 100 mph, which after hitting the Earth’s surface move laterally at 100+ mph. This can make for exciting times when hiking through forested areas as trees are being blown down, or trying to climb a cliff face while experiencing similar winds.
Storms are also sometimes forming much faster. For example, in 2013 when Oklahoma City experienced two EF-5 tornadoes within several weeks, the second one formed from what was a blue sky 30 minutes earlier! Also forming are increased downpours / heavy rains. Thunderstorm losses increased 500% from 1980 to 2011 according to giant insurance re-insurer Munich Re.
For hikers, not only floods, but flash floods present an ever increasing danger. These can be caused by rain events miles away from an area being hiked in and come rushing in unexpectedly, sometimes causing deaths (such as noted in Zion National Park in 2015 when 7 experienced hikers were killed in a flash flood).
Even on very steep slopes the danger can be great, as was seen in the deaths of a very experienced mountain climbing husband and wife who were struck by a rock and mud slide while climbing on Crestone Needle, a 14.000’ mountain in the Sangre de Christo mountain range in Colorado in 2010. They had started their climb with totally blue skies.
On steep slopes and cliffs rockfalls are more common now, due to both, moisture getting into cracks and heating / cooling (expansion / contraction) of rocks with cracks.
During storms lightning is often created, and research published in the journal Science indicated as the planet warms there is an increase in lightning strikes. The hazard to hikers, and anyone outside for that matter, is increasing. Colorado is a state with lots of people outside in the open, hiking, and that state has the 3rd highest annual rate of people being struck by lightning (Florida is 1st and Texas ranks 2nd). For example, in 2015 36 people were struck by lightning in Colorado. Handily, only about 10-15% of people struck by lightning die. But, on the other hand, most survivors are severely injured, with the majority sustaining long-term injuries, including nerve and muscle damage, such as numbness and weakness in the limbs, temporary or permanent paralysis, cardiac arrest, concussions, seizures, blown out ear drums, and cataracts. Many also suffer severe psychological changes. Any moisture on the body is instantly changed to steam, resulting in burns and things like shoes or clothes being blown off. Metallic objects like zippers, cell phones, iPods with ear phones can cause burns or explode due to being superheated by the lightning.
On July 17, 2015 I was hiking in the San Juan Mountains on McMillan Peak with a group, as weather began to move in from the south. Lightning started to occur to the south, and I became a bit concerned. A discussion with the trip leader resulted in us turning back just below tree line.
Within minutes, lightning was striking the ground in the area above tree line that we had been headed for. A bit later that day 4 hikers were struck while hiking on Mt. Yale just above tree line, and 1 died. A month later (August 18) a friend of mine was struck by lightning while hiking in the wilderness a few miles west of where we had been hiking. He survived, but his life has been severely altered.
And, last but not least, due to damage to the ozone layer by the release of bromine and chlorine pollution, we area seeing substantial increases of UV-A and UV-B, which is resulting in lots more sunburn, skin cancers, and cataracts. The numbers go up greatly as you get to higher elevations, such as when people hike in mountains (For example, hiking in the mountains of Colorado provides a 400% increase in UV radiation when compared to walking in New York City). Every year there are more new cases of skin cancer than the combined incidence of cancers of the breast, prostate, lung, and colon! I must admit to being a poster child for this, as I have been hiking at high elevations for over 50 years and piloted gliders to altitudes of 18,000 feet above sea level for 20 years. Skin cancer removal surgery has become an annual event for me. I’ve retired from gliding, but still thoroughly enjoy hiking the hills and bagging the peaks as often as possible, but still pay a price. Sun screen and protective clothing / hats help, but much damage is already done in earlier years.
We will continue to have many fun, safe hikes and mountain climbs, but…… With a changing atmospheric chemistry and warming world, a NEW NORMAL will be seen in weather…….. EXTREMES….
Very rapidly forming storms
High intensity rainfall
Floods – both river floods and flash floods
Hail – bigger and greater volume
Wind – increases in high velocity
Blizzards / Extreme cold
Heat waves, Record High Temps, High night low temps
Sunburn, skin cancers, and cataracts
There is nothing you can do about the weather, so just adjust your activities to it. Check weather forecasts before you set out on your activities, and keep your eye on it as the day passes. Be aware. Be careful. And continue to safely enjoy the good days for hiking and climbing.