Climate Research

by
Enric Palle Bago
See also:
Armagh Observatory Climate Series
Global Warming at a Glance
The short story I am going to try to explain here a story, the story of what I am doing in a way in which I hope everybody (including non-scientists) can understand. I will use the sentence "an image is worth a thousand words" as my main philosophy, but small explanations of the image links are still necessary. After looking at an image I recommend the use of the back button to return to this page so you do not have to use the scroll bar all the time. I also recommend looking at all the pictures, because they are chosen to give a particular impression, the impression that our planet is a small ball of dust floating in the vast space of our galaxy and that the climate system is one of the most complicated problems of today's science, but at the same time one of the most beautiful to observe, not only to the scientific eye. Bear in mind that the real story is not so simple, and for the experts in the field not everything in this page is entirely true in the sense that small exceptions are not taken into account and detailed explanations are not attempted, but for the non-scientists, you are not going to learn anything incorrect. I also have avoided any kind of speculation. Our story has then two main characters, the Sun and the Earth. The Sun is a star about a 10⁸ times bigger than the Earth, and in its interior enormous amounts of energy are generated via nuclear reactions. This enormous machine, releases to space vasts amounts of energy. The Earth receives a very small part of this energy, but enough to be able to support life. The Sun is in fact the power engine of life on our planet. Because of the spherical shape of the Earth, the amount of energy received from the Sun its bigger at the equator than at the poles. In the same way as two bodies at different temperatures tend to transfer the heat from the warm body to the cool when they are put in contact, the energy received from the Sun is redistributed all over the Earth. The heat is transported from the equator towards the poles, through big masses of warm water in the oceans and air in the atmosphere. The pattern of those movements gets more and more complicated and they trigger the whole climate system and the weather at any particular point of the Earth. The Sun and its activity cycle. The Sun may appear as a very quiet body which dances in the sky every day in a very regular pattern. But the truth is that the Sun is far from quiet, in fact it is always changing, on all time scales, from millisecond to millions of years. The Sun was born (some 5 billion years ago) and it will end its days some 5 billion years more in the future taking with it half of the planets of the solar system (the inner ones). Throughout its long life it will experience changes in almost all of its features - radius, luminosity and temperature, but the changes are so slow that for all practical means it is constant for life in Earth. Or more particularly for our question, which is how the Sun is going to influence the Earth's climate in the last 100 to a few thousand years. However the Sun does vary on time scales shorter than the stellar evolution. The sun changes in a very well-known cycle of eleven years, known as the activity cycle or the sunspot cycle. A sunspot is a big region of the Sun which looks darker than the rest of the disk. In fact the sunspots are very bright, but the slightly brighter background of the Sun's surface gives them their dark appearance. The sunspots are manifestations of the magnetic field of the Sun, the activity cycle is in reality a magnetic cycle. At the beginning of the cycle, the minima, there are almost no sunspots on the Sun's surface, but slowly some appear near the equator in both hemispheres. Their number increases and at the same time they move slightly from the equator towards the poles. At maximum activity (around 4-5 years after the minima) there are usually a great number of sunspots covering the Sun's disk. Then, a little slower than they started to appear, they start to disappear and we return to a new minima. This cycle is repeated again and again approximately every 11 years, however the exact duration is not constant and it has been seen to vary between 9-13 year. The intensity of the cycle (number of sunspots) is not constant either. During this cycle more things are going on in the Sun. Violent magnetic storms accompany those sunspots and the whole magnetic structure of the Sun gets disturbed. The Sun is continually releasing energy into space in the form of electromagnetic radiation (or light), but also in the form of charged particles, what we call the solar wind . However at certain times, more frequent near the solar maximum, the energy is released in violent bursts that we call flares or coronal mass ejections . It is generally difficult to imagine the size of those massive explosions but the image to the right shows a magnetic loop compared to the size of the Earth (remember the Earth is not really that close to the Sun, that's a comparison picture). The Earth and the climate system The Earth is a planet with an atmosphere that retains some of the heat from the Sun and gives us a comfortable 15 degree mean temperature. The atmosphere is extremely thin , but all the weather phenomena we know occur in this bottom layer up to about 15 km. Higher up the atmosphere becomes less and less dense until the vacuum of space is all that's left. This atmospheric heat trapping is known as the Greenhouse effect and NO, the greenhouse effect is not produced only by mankind, as people tend to think reading the news papers. The greenhouse is a natural effect carried out mainly by the water vapor in the atmosphere, some other atmospheric gases like CO₂, NO₃ also contribute to this effect but their concentrations are so small that their effect is small compared to the water vapor. And here we go, global warming is one of the main puzzles in today's science. The global warming theory basically says that the Earth is warming, temperature records at many places of the world have been taken during the last 200 years, although at most of those places only during the last 50-100 years. When global means for those records are calculated it looks like the Earth's global mean air temperature and sea surface temperature have been increasing since the second half of the 19th century until the present. Since approximately the second half of the 19th century (1850), we have been in a post industrial revolution society. The consumption of carbon in industrial ovens, car engines, forest burning, and other factors, releases CO₂ into the atmosphere and those kind of activities have been increasing since the industrial revolution. Thus the amount of CO₂ gas released into the atmosphere has been increasing since approximately 1850. Now, the Greenhouse Theory, not to be confused with the greenhouse effect, says that due to the increase in CO₂ in the atmosphere, and due to CO₂ being a greenhouse gas, the greenhouse effect is becoming stronger due to extra CO₂ and thus the Earth's temperature is increasing. If that is true, the problem is not immediate, but since the predictions for the next century are that we will keep releasing CO₂ into the atmosphere at an increasing rate, it is evident that the temperatures will continue to increase leading to many problems. The temperature of the Earth has increased about 0.5 degrees centigrade during the last 100 years. Yes, only that, a small amount that you would not notice in the street, but when it becomes a global increase then its a quite respectable quantity. The predictions for the next century are of all kinds, but it would be reasonable to assume a 2 degree increase in temperature during the next 50 years, and that would have some nasty effects. Examples: coral destruction throughout the world, ice sheets melting in the poles leading to increase in ocean level leading to inundation of land and cities near the oceans, BUT do not believe blindly in those predictions, global warming has been claimed to be the end of the world but I regard that as being a 'little' exaggerated. There are still many uncertainties in our knowledge and the greenhouse theory even though it is very rational and plausible has not yet been undoubtedly proven (if this is possible). The Earth is a very complicated system and many feedback mechanisms may still not be known. I admit that lacking a more plausible explanation the greenhouse theory looks as the most plausible answer to me, but I also think that other factors like solar activity are involved in the problem. There are too many things that we still do not know and many answers are lacking. The Earth is a very complicated system with volcanoes, earthquakes, storms etc which will also have their effect on the climate system making more difficult the task of recognising global warming. And now I will introduce a small character whose possible role in global warming we will discuss later: the clouds. No doubt you are tired of so much lecturing, so let me show you first how beautiful they can be in this image of some clouds together with Mercury . The clouds are a main character in the climate scene, however their detailed role is yet to be determined. Climate models do not know how to deal with them. They play a double role, one the one hand they are bright and they reflect part of the radiation coming directly from the Sun back to space, having a cooling system because less energy arrives to the Earth surface. But on the other hand the Earth releases to space energy too and clouds can act as a blanket, trapping that radiation which should have escaped to the space in the same way as the greenhouse gases. Which of the two effects is going to dominate depends on the type and altitude of the cloud. Thus assessing their role in climate becomes nightmarish. It is believed though that in general, high cloud tends to warm the climate whereas low clouds tend to cool it, and that clouds in general have a cooling effect.
The Solar-Terrestrial Relationship And how is solar activity felt on the Earth? The answer is: in many ways . The increase in activity triggers an increase in the Sun's brightness (electromagnetic radiation or light) and the violent phenomena that occur more frequently during epochs of high activity release strong fluxes of energetic particles towards the Earth. The particles fluxes are charged and due to the magnetic field of the Earth, are deviated (in a quite complicated way) and strike the Earth at the poles. Those particles entering the atmosphere release all their energy when colliding with the top of the atmosphere and produce the aurora . Aurorae are frequently observed near polar regions in both hemispheres and are one of the most beautiful displays produced by nature. They can also be seen from space . Here are a couple of beautiful displays: aurora and planets , aurora and telescope and aurora multicolor . However those particles also damage satellite detectors and cause satellites to fall down to Earth. They can also shut down electrical lines and cause communication problems. And even though we are safe on Earth protected by our atmosphere that radiation can be fatal for astronauts in space. The changes in the electromagnetic radiation are also felt on the Earth, the properties of the top of the atmosphere being affected by changes in ultraviolet radiation. Why do some people believe in the Sun playing a role in climate? Solar activity has changed during the past centuries, the cycles are now shorter and more violent than they were a hundred years ago, and when the Sun is more active, we know that it is brighter. The number of sunspots has been observed by astronomers since the 16th century and the behavior of solar activity resembles the temperature records on Earth. The period from approximately 1680 to 1750 is known as the Maunder Minimum, a period when the sunspots disappeared from the Sun's surface. This same period coincided almost exactly with the very cold period on Earth know as the Little Ice Age, suggesting that the decrease in the Sun's brightness was somehow transmitted down to Earth. However, at least for the last century, the changes in brightness alone are too small to explain the total increase in temperature but the greenhouse hypothesis alone can not explain the temperature behavior either. The ups and downs look like solar activity, but the total amount suggests a CO₂ effect. A combination of both is the probable answer since before the industrial era, temperatures were also changing and cannot be blamed on mankind. The important question now seems to be what is the contribution of each of the two factors. The Clouds and the Galactic Cosmic Rays The galactic cosmic rays is the name that we give to the very energetic particles which arrive from outside the solar system. The cosmic rays are indeed very energetic particles traveling at speeds sometimes near to the speed of light, even though their energy range and speed is quite wide. It is believed that these particles form during supernova explosions and similar energetic events. Because they are charged particles, they are affected by magnetic fields, which accelerate and deviate them from their original courses. The result is an isotropic cosmic ray distribution of cosmic rays entering our solar system. Our Sun has a very strong magnetic field, and this magnetic field acts as an umbrella for those particles, an umbrella however that has some holes. Because the Sun's magnetic field has to be overcome, only the cosmic rays with an energy high enough to overcome that repelling force are able to penetrate the solar system. Some of the particles that penetrate into the solar system, will eventually collide with the Earth (and the other planets) and will penetrate down through the atmosphere and, depending on the energy, even underground. In this way, we are continuously receiving showers of cosmic ray particles. These particles interact (collide) with the atoms and molecules in the atmosphere and produce a vast quantity of other particles (Cosmic ray showers ) less and less energetic all the time, so the original energy produces ionization (in a very simplified way) in the atmosphere. When there is high activity in the Sun, its magnetic field is stronger and the number of particles able to penetrate the solar system is smaller. That is reflected also on the Earth, where we see a decrease of those particles reaching the atmosphere, Sunspots-Cosmic Ray Flux . The decrease occurs in phase with the increase in the sunspot number (or the activity). Until a few years ago cosmic rays were not believed to have any effect on the climate system, but a team of Danish researchers published in 1997 a correlation between the cosmic ray flux measured at ground level and the amount of clouds in the sky. A correlation means that the two datasets vary at the same time, it means that when there are more cosmic rays, there are more clouds, and vice versa, however it does not necessarily imply that there is a relationship between them (both things could be caused for example by the sunspot number, very unlikely). However the cosmic ray flux is the major cause of ionization in the bottom of the atmosphere where the clouds form, so it is not unreasonable to think that the amount of available ions will affect cloud formation. The implications of such a mechanism, in simplified terms, would mean that when the activity of the Sun was lower during the past century, the cloud amount was higher and that, with the increase of solar activity during the 20th century, a decrease of cloud cover has also occurred. Since we saw that clouds cool the Earth, a decrease in cloud cover would mean a decrease in cooling and consequently an increase in the mean temperature. We have found then a way to explain global warming (or at least part of it) without intervention of the CO₂ gases. Up until now no one has been able to demonstrate that theory to be false, but no one has proven it to be true either. Both things are proving to be equally difficult. In the first place there is still no physical mechanism to explain how the increase in ionization would lead to an increase in cloud formation, but the present knowledge of cloud microphysics is still rather poor. Also the role of the clouds in climate is not well understood. Cloud warming or cooling will depend on cloud type, altitude, reflectivity, droplet size, and the changes in cloud cover will vary in latitude and longitude (see here a map of water vapor over the oceans which is not necessarily cloud, but gives an estimate of how complicated is its distribution). In different parts of the Earth different cloud types are more frequent. The other major problem is the lack of cloud data. Data suitable for this study has to be global coverage data (satellite) and satellites have been out there for only around 20 years and the length of the solar cycle is 11 years, so we have only a little bit more of a cycle than satellite cloud data, and that makes things rather difficult. The data from satellite are difficult to calibrate and long datasets are not exempt from problems. Look for example how difficult it is to distinguish between clouds and ice . Note: The images displayed on this page have been taken from many sources, mainly the internet and I have not always remembered and properly credited, particularly when the images are not signed. I sincerely apologize for this fact and invite anybody who feels uneasy or does not want me to use their images to write me and I will promptly repair the error.

Last Revised: 2009 November 2nd