- 3549 - GLOBAL WARMING - what can we expect? Global warming can be understood. Although, it is complicated. The system has many feedback loops both positive and negative. There are long time constants between causes and effects. But, the physics is known and if we understand the complexities well enough we can understand climate change and we can make accurate projections for the future.
--------------------- - 3549 - GLOBAL WARMING - what can we expect?
- The physics all starts with our Sun which is and has been the source of all our energy. Both the Sun and the Earth are treated as blackbodies in absorbing and reflecting energy. The Sun has a radiation temperature of 6,000 Kelvin. The Earth has a reflection radiation of 300 Kelvin, 33 C.
-
- The radiation from the Sun is 500 nanometers peak wavelength, called shortwave radiation by the environmentalists. This is ‘green light” to us laymen. The Earth has 1,000 nanometers peak wavelength radiation. The wavelength is longer and the energy is lower. This is in the infrared region of the spectrum and called longwave radiation.
-
- Radiation from the Sun heats the atmosphere of Earth and heats the surface. If we start with 100 watts of the Sun’s energy striking Earth, only 20 watts gets absorbed by the surface, mostly by the oceans. 30 watts gets reflected back into space, mostly due to cloud cover, or snow.
-
- That leaves 50 watts that is absorbed by the atmosphere. It is the heat in the atmosphere that keeps us warm. Now if we add greenhouses like, carbon dioxide, water vapor, or methane things change. CO2 absorbs energy at 1,500 nanometers and at 4,300 nanometers wavelengths.
-
- With these gases in the atmosphere more energy is absorbed and more energy is reflected back to Earth to be reflected again and sent back in to the atmosphere. The net effect is that only 20 watts get reflected back into space. An additional 10 watts is absorbed into the atmosphere due to these greenhouse gases and that is global warming.
-
- By studying ice cores in the Antarctic physicists have recorded that amount of CO2 in the air bubbles trapped in the ice over the last 400,000 years. They have also recorded the temperature by analyzing the amount of deuterium in the ice air bubbles. Over this 400,000 years the CO2 concentrations have varied between 200 and 300 parts per million in cycles spanning about 80,000 years.
-
- Methane concentrations track these same cycles only between 400 and 650 parts per billion ( note 1,000 times less). The temperature tracks these same cycles as well with variations of + or - 0.75 Centigrade. That is until the last 2,000 years.
-
- Since year zero the CO2 concentrations have steadily risen to 380 ppm. And, methane has risen to 1750 ppb.
-
- The oceans have already absorbed enough additional energy to raise temperatures 0.5C for the next 20 to 30 years even if greenhouse gas emissions ceased today. That is heat in the pipeline. The ocean provides a long time constant for climate change.
-
- 0.5C is the mean temperature increase over the next 100 years but the standard deviations of temperature about that mean will be even more extreme. The temperature rise sets off positive and negative feedbacks that puts greater cycles into the system.
-
- Now, it is very unlikely that human kind will stop CO2 emissions today. The more likely scenario is that CO2 emissions will continue to grow from 380 ppm to 680 ppm and that will mean the average temperature will increase +3.5C over the next 20 to 30 years. And, the standard deviations about this average will be even more wild. In the next 100 years temperature could likely increase by 6 to 7C.
-
- The biggest problem with these scenarios is that they set up positive feedback in the system. Warmer climates beget even warmer climates, and wilder fluctuations in the weather.
-
- Water vapor is a greenhouse gas also. Warmer oceans mean more evaporation and more water vapor in the atmosphere. More greenhouse gas in the atmosphere means warmer temperatures and more evaporation. When snow melts there is less reflection and more absorption of energy. The additional heat melts more snow. The positive feedback makes the glaciers melt even faster.
-
- All the feedback in the physics is making the climate get warmer. If left alone the eccentric orbit about the Sun would bring on another ice age to Earth. But, this is unlikely because CO2 will cancel that out.
-
- The warming effect is greatest at high altitudes and at the poles. Have you ever wondered why it is colder in the mountains where you are closer to the Sun? It is because the air is thinner in the mountains and it is that atmosphere that absorbs the Sun’s heat.
-
- There are many other affects from climate change besides warmer temperatures. There are biological effects from disease bacteria to polar bears. There are the marine life changes caused by increased acidity in the oceans. There are rainfalls and drought changes. Crop failures and floods.
-
- All these are in a system of positive and negative feedback loops with long time constants that once started are far out of our control. Once the environment is wildly out of control we are just in it for the ride.
-
- If we did do something to change climate change what would it be?
-
---------- 1. The single most effect impact would be to increase energy efficiency. We waste so much energy that could be salvaged quickly with increased conservation and efficiency.
-
------------ 2. Adopt alternative energy sources, get away from burning fossil fuels as quickly as possible.
-
----------- 3. Develop methods of carbon capture to pump carbon underground so it does not get into the atmosphere.
-
----------- 4. Seed the atmosphere and the snow with compounds that would reverse the processes providing negative feedback. This is a very tricky alternative because there are likely severe side effects that we can not anticipate. We could create more problems than we solve.
-
- All the more reason to understand the physics. And, let the science make the best decisions, not the politicians.
-
April 19, 2022 GLOBAL WARMING - what can we expect? 908 3549
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
--------------------- --- Wednesday, April 20, 2022 ---------------------------
No comments:
Post a Comment