We mentioned in The Water Planet Lesson 3 that over the last few decades we have heard the term climate a lot. In most cases that was in reference to climate change.
This term is puzzling. We just explained how the oceans partially influence our climate, making the southeastern United States warm and humid. The term climate change suggests that this would change.
How could it change?
The warm ocean currents slide across the Atlantic and up the east coast of the U.S. helping to bring the warm humid conditions we are known for. Could this change? We will look in a later topic this year at the forces that drive these currents, but the rotation of the earth is one of them. Has the rotation changed? What changed to make the climate change? Following the nature of science – we know that the process begins with observations, which leads to logical explanations (hypotheses) that can then be tested. What observations have led to the idea that our climate changes?
One climatic change that people have talked about are events called ice ages. We have all seen the movie with the cute mastodon and saber-toothed tiger. The logical explanation (hypothesis) is that the last ice age occurred during the period these animals were on the planet – about 13,000 years ago. What led to this idea?
Fossils to start with.
We have found fossils of these even in Florida. What we know of them suggest they were designed for colder climates, just like if we were to find the fossil of an old yak in Pensacola today. We know what kind of climate yaks prefer – polar – and this would suggest that Pensacola was colder. Now no yaks have ever been found here, but mammoths have been found in the Florida panhandle.
When I was in college at Troy, we would drive out into the country, find one of those roads that cut through a clay hill and pull off. Going over to the clay roadside we would begin to dig through. We found fossil echinoderms – sand dollars and sea urchins. We found mollusk shells of marine species and even some corals. This suggested two things. 1) That this part of the U.S. continent was once under the ocean. 2) With corals growing here, it must have been warmer. Not too far away from these sites a group from Auburn found the skeleton of a large whale. Further supporting this thought that the sea level was once much further inland than it is now, and, at that time, Pensacola must have been beneath the Gulf of Mexico.
To add to this, remnants of terrestrial habitats have been found on the present submerged continental shelf off our coast. Recently stumps of an old cypress forest have been found on the bottom of the Gulf just offshore of Pensacola and Mobile. This suggest that at one time the beach was much further south of where it is currently. It suggests that sea levels rise and fall over time. The explanation for this is the climate has changed over time.
What about the ice?
Observing glacier movement and impacts during our current time suggests that these same forces could have formed some of the geologic features we see in the temperate regions of the planet today. It is believed that sheets of ice from the polar regions may have reached as far south as Indiana and Kentucky – forming the Great Lakes and making the climate of the southeast much colder. Alpine trees would have grown here, and large colder weather animals would have roamed the landscape. Fossils suggest this did happen, and they have been able – using radio-isotope dating – to date when these events happened.
During these ice age periods, water from the Gulf of Mexico would have been frozen into the ice sheets, lowered sea level several miles south of where it is now. It would have placed Pensacola much further from the coast and it is believed the bays we know now would have been woodland areas where rivers were flowing towards the Gulf. When the ice age ended, the ice would melt. A tremendous amount of ice melt would have flowed south towards the Gulf, filling the low “canyon” like areas to form our bays, and gouging out areas where the current flow was high forming the bluffs along Scenic Highway. The melting ice from around the planet would cause sea level to rise and the beaches of the prehistoric Gulf of Mexico would begin to move inland, covering ancient cypress swamp forest with seawater – killing them. If this were true, then we should find fossils of inland, or coastal species offshore – and we have.
With these observations staring us in the face, it is easy to understand why most scientists believe the planets climate has changed over time, and that climate change is real. But was this a one-time thing? Did it happen earlier in history? Is the sea level rise and fall a pattern like the rising and falling tides we experience today?
It seems so.
Looking at graph 1, you can see an up and down pattern of sea level over the 400,000 years. It does seem to make a pattern similar to the high and low tides over the period of a month. Again, this supports the idea that the climate of the planet does change, and that the southeast may not have always been warm and humid. But the next question would be – why does this happen? The orientation of the planet to the sun does not change… the rotation of the earth does not change… or does it?
A logical explanation would include a rise and fall in temperatures – global cooling and warming periods. But what would be make the temperatures rise and fall that much?
This becomes an interesting part of science. The next step would be to develop a test for the logical explanation you have developed. This explanation is that the overall temperature of the planet cooled – the polar climate reached closer to the equator and allowed ice formation as far south as Indiana. How do you test this idea?
At this point we should introduce another term you have probably heard – the greenhouse effect. For many this is a term that means the planet is warming and things are bad. We will get to why they are saying this later, but I will say now that the greenhouse effect is something that has allowed life on our planet to exist. Without it our climate would much colder and life would be limited, if here at all. So, what is this greenhouse effect?
As the name implies, it is a warming effect. Many of us have experienced the significant warming within a greenhouse. We build these to keep certain plants from getting to cold during the fall and winter. The idea is that the suns UV rays can easily penetrate the clear glass of the greenhouse. Once inside this energy heats the air within, increasing the temperature. Warm material rises but the warm air cannot escape through the glass as the light rays could penetrate it. Over time it gets warmer and warmer inside. There are usually glass windowpanes that can be opened to release some of the hot air so that it does not get too hot inside. Some greenhouses have vent fans. It is believed the same is happening on our planet.
But there are certainly no glass panes holding the warmed atmosphere in. What is doing this?
Enter… greenhouse gases.
The lower portion of our atmosphere is made of many different gases – mainly nitrogen and some oxygen – but there are others. 1% of those gases are what we call greenhouse gases. These would be carbon dioxide (CO2), methane (CH4) water vapor (H2O), and nitrous oxide (N2O). Experiments in the lab have shown that these gases can, and do, hold heated air close to the surface – warming the planet and allowing life to exist here. It was first recognized by a Swedish scientist (Svante Arrhenius) in 1896. And this is a good deal.
So, another logical thought… (hypothesis)…
If the levels (concentrations) of these greenhouse gases change over time – the greenhouse effect would change over time – and the climate would change overtime. Good idea right? But is it true?
Should be easy enough to test.
Set up a series of experiments (n=a whole bunch), account for your control and constants (see lessons on the nature of science) and alter the concentrations of greenhouse gases within your test chambers. You can alter all of the greenhouse gases at one time, alter individual ones at different times, there are numerous interesting experiments you could do. The concentration of greenhouse gas would be your independent variable. Your dependent would be the air temperature within the chambers. Run many trials – this should be easy to do and give you good results you could feel confident about.
Yes, as you increase the concentrations of the greenhouse gases you will increase the air temperature. The greenhouse effect is occurring on our planet.
But do these greenhouse gas concentrations really change over time?
Enter the ice cores…
As water freezes into ice it forms small air bubbles within the ice. You can see these. Our assumption is that the gas within these air bubbles is atmospheric air and was entrapped at the time of the ice formed – and this assumption would be true.
If this is so, could we extract ice that was formed a long time ago – remove the gas from the air bubbles formed at that time – and analyze this gas for the concentration of greenhouse gases?
Makes since on paper, but how would you do this?
Enter – technology…
We discussed the importance of this in the nature of science lessons. Without the development of technology, we just cannot do the scientific experiments we would like to do, and science cannot advance. But we are good at developing technology and we have been able to develop instruments that can carefully pierce the air bubble of an ice cube and extract the gas WITHOUT contaminating it. Amazing really – but then we can also pierce the nucleus of a cell and manipulate the DNA within… amazing still. We also have instruments that can analyze what gases are within this air bubble and at what concentrations. So, now we need “old ice”.
Where do we find “old rocks” when we are looking fossils?
We dig deeper. The argument is the older rock is deeper in the earth and new rock/sediment has been laid on top. We have now learned, because of plate tectonics, that this is not always true. The earth bends and buckles and, at times, older rock is above newer – but they have developed technologies that can age the rock – so, we are good there.
Can we dig deeper into the ice to find “old ice”?
Yes… at the poles. Scientists have been collecting ice cores for decades and have been able to analyze the gas bubbles within the different layers of the ice.
Do the results suggest that the concentrations over greenhouses fluctuate over time?
Yes… they do.
So, when greenhouse gas concentrations decrease – our planet becomes colder – ice ages occur – and sea level drops.
When they increase – the planet warms – ice melts and sea level rises.
They have been able to graph the greenhouse gas concentrations over time as well as the sea level over time and observe a strong correlation – a strong cause and effect scenario.
What about the temperature?
Can you determine the temperature of the planet during these period in an ice core and graph those?
Not exactly. However, you can conduct experiments that will show you that IF the greenhouse gas concentration is at “X” then the air temperature within the test chamber is at “Y”. To feel confident that a greenhouse concentration of “X” will produce an air temperature of “Y” you would need to run many experiments (n= a whole bunch) and have very little variability in your results (the mean would be pretty close each time). And they have.
Another useful piece of information is finding spores and pollen within these ice cores. Some scientists are excellent at identifying what type of spore or pollen grain is in the ice. Knowing what kind of plant produced it, and what kind of climate those plants like, you have a better idea of what the climate was like at the time that ice, or sediments if you are analyzing those, formed.
All of this information are presented in scientific papers and at scientific conferences. Ideas and suggestions are bounced off of each other and more experiments are conducted raising our confidence level of what the climate of our planet was like in the past and that it is, in fact changing.
Right now… we are in a warming period. Air temperatures are increasing, and sea level is rising.
But what about the argument that humans are causing this now?
You just continue looking at the data we currently have been monitoring.
Yes, CO2 levels are increasing – as are the other greenhouse gases.
Yes, global air temperatures are increasing.
Yes, ice sheets are melting, and sea level is increasing.
All to be expected during a warming period.
The difference… the rate of change.
If you look at a graph of CO2 concentrations over time above, you will see the changes over the last 800,000 years. You will see a steady up and down trend between 180 and 260 ppm. There are two higher peaks near 300 ppm about 325,000 years ago and another about 125,000 years ago, but most are in the 180-260 ppm range.
Then look at our current levels – on this graph about 1950.
In a VERY short period of time we exceed the 300-ppm level and are heading towards 400 ppm. This has not happened in the last 800,000 years. Yes, we are in a warming trend, ice is melting, and sea level is rising – but never like this.
What is different?
This intense increase in CO2 would suggests that the earth’s temperature would also be rising.
And it is – see the NOAA illustration on temperature change since 1880.
If you follow the news you probably have heard that the warmest recorded temperatures have all been in the last few years, and it seems we break a record some month every year.
It appears that the warming trended we are currently experiencing is like no other we have seen. The rate is faster than we have ever seen. What is different?
Humans… and our consumption of fossil fuels. The birth of the industrial revolution and the spike in CO2 match well on a graph.
The extraction, processing, and consumption of fossil fuels significantly increases CO2 levels in the atmosphere. AND if CO2 increases, we know what will happen with temperatures – and it appears to be happening. This is a very logical argument, and most scientists agree with it.
But there are huge amounts of CO2 released during volcanic eruptions – the planet has seen this before. How did the planet recover?
There are systems within the planet that remove CO2 (and other greenhouse gases) from the atmosphere. Plants in particular are good at this – but there are others. As CO2 increases, the planet warms, as the planet warms the climate becomes more conducive to plant growth and there is an increase in plant growth and area covered. With more CO2 in the atmosphere there is more “plant food” for photosynthesis – CO2 + H2O à C6H12O6 + O2. So, the plants begin to withdraw CO2 from the atmosphere. Making less greenhouse gas – which makes the planet colder – plants do not like this so much (many of them). With less CO2 there is less “plant food” for the plants – so we see a die off of plants. Now that the plants are reduced, the CO2 begins building again and so the cycle continues.
So, you would think with such an increase in CO2 in the last 100 years – the plants on the planet would jump into overdrive and draw these large CO2 concentrations (+300 ppm) from the atmosphere.
But we are removing plants and trees from the surface of the planet at an alarming rate. We need agriculture land – forest must go. We need land for homes, offices, and airports – forest must go. We need money from forest products – forest must go. With the decrease in plant coverage so goes one of our natural remedies to excessive CO2. AND the process of converting forest to farmland, cities, and wood products utilizes fossil fuel burning technologies – adding to the increase in atmospheric CO2 – which adds to the increase air temperatures we are seeing.
Can the oceans help remove CO2?
I mean 70% of the planets surface is ocean – can the ocean absorb/reduce these CO2 levels?
CO2 is absorbed by the sea and converted into carbonic acid.
CO2 + H2O à H2CO3 (carbonic acid)
H2CO3 à H+ + HCO3 (bicarbonate)
This increase in carbonic acid – due to increase CO2 absorption – decreases the pH and makes the ocean more acidic. This is known as ocean acidification and it is occurring now. A decrease in pH can make the waters too acidic for shell formation (acid dissolves limestone – CaCO3) and this is what mollusk and corals use to produce their shells. So, these creatures (corals reefs) are in danger of being dissolved with ocean acidification.
So, yes – the planet can help reduce the concentrations of CO2 in the atmosphere but at a cost. AND we are removing many of the plants and animals that conduct this carbon sequestration, so it is not being removed – SO levels of CO2 and air temperatures continue to rise at record rates.
So, what will happen if this upward trend continues on the map?
Here is where computer models come in.
Today, MANY scientists are trained in computer model development. Good models help predict potential outcomes that can be used by resource managers and decision makers to make decisions now to either enhance or stop practices that could produce outcomes we want.
Computer model development is not easy. The models are only as good as the information you give it. So, the scientists must think long and hard on what information to give the model AND be able to obtain that information.
Hurricane forecast models are a classic example of how this works.
We know what hurricanes feed on. Needed data is collected by hurricane hunters and fed into the models. We see the predictions of these models on the evening weather as “spaghetti” model lines. Each color you see on the TV is a different model and what they predict. Sometimes the spaghetti lines are all over the place – suggesting that the models do not agree, and the weather forecaster is not sure where it is going. The nice thing about this, is each time they post a model, we do see where the storm goes. You get a result very quickly. If your model is wrong – you go back in and correct what was wrong. Then you wait for the next storm and see if your model is better. Some models are very good, and forecasters have learned which models they feel more confident with and focus on those. Sometimes all of the models align, and the forecaster’s confidence is very high on where the storm is going to go. Storm intensity models are not as good as locations models at this time.
But with climate change predictions, we do not get instant results. The predictions are 30 – 50 – 100 years out, and we will not know whether the models are correct for some time. Do they feel confident about their models? Some do, and some do not. But some things currently occurring in our country are beginning to give us an idea how well the models are working.
Within the models we can feed CO2 concentrations, air temperature, forest coverage, ocean pH, the ability for farm crops to remove to CO2, the release of methane from livestock, all sorts of information. And then adjust the numbers for different scenarios to see what the model will predict.
Here are some predictions from a text published in 2011.
Increase in air temperature of 3.6°F and CO2 concentrations to 450 ppm
– Forest fires will worsen
– Prolong droughts intensify
– Deserts spread
– Major heat waves more common
– Fewer winter deaths in higher latitudes
– Conflicts over water supplies increase
– Modest increases in crop production in temperate regions
– Crop yields drop 5-10% in tropical Africa
– Coral reef bleaching increases
– Many glaciers melt faster and threatened water supplies for up to 100 million people
– Sea levels rise enough to flood low-lying coastal areas
– More people exposed to malaria
– High risk of extinction for Arctic species – such as the polar bear
Any of these sound familiar?
Because of this, many are feeling more confident about some of the prediction models and are urging decision makers to pay attention and make changes.
For us, they are predicting that the drier places will become drier – and the wetter areas will become wetter.
There is no doubt, at the moment, the U.S. southwest is drier. I camp out there in the summer and many areas have little water, water use restrictions are everywhere, and many locations simply do not have it. We learned very quickly how to conserve water while camping for a month.
This same part of the country is experiencing record number of wildfires. It has become a regular part of life out there – be prepared, it is coming – are you ready?
Here in the southeast we have seen record rains and flooding. Pensacola is known for lots of rain – typically 60-61” each year. But in recent years we have hit 90” and in 2014 we had a record 24” in 24 hours. Hurricanes are becoming more numerous – reaching deep into the Greek alphabet to name them all – and some communities, who use to experience hurricanes once a decade, are now seeing them once a year. This year Lake Charles LA saw two in one year.
We can also add to this story the tropicalization of the northern Gulf of Mexico. Tropical species, such as hogfish, manatees, and mangroves, are now dispersing further north. At one time, our winters were too cold for them. Now many are surviving the warmer winters and moving into our area. This could pose a problem for invasive species as well – those that use to be restricted to southern Florida might be able to survive in the panhandle in the near future.
The climate… it is a changing…
Creating a greenhouse effect.
If you have the supplies this would be interesting.
Go outside in the morning, place a few thermometers on the sidewalk (important – place ALL thermometers on the sidewalk, do not place any on the grass, CONSTANTS), cover half of the thermometers with some sort of glass, leave the other half in the open air. Measure their temperatures every 15 minutes for maybe two hours. Graph the temperature increases (dependent variable on the “y” axis). Calculate the mean temperature of those covered with glass and those that were not.
Do you see a difference? Do you see the “greenhouse effect”?
Creating air bubbles in your ice cubes
Most homes have ice makers in their refrigerators now. You can take these ice cubes and look at them closely to see the air bubbles that formed during the ice formation. BUT, if you have ice trays that you can fill with water and make your own ice this will a) allow you to SEE the formation of the air bubbles, and b) will be more fun 😊