The two major constituents of the Earth’s atmosphere, nitrogen and oxygen do not contribute to atmospheric warming due to their molecular structure. The most important greenhouse gases that occur naturally in the atmosphere are water vapour (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ozone (O3). The most important greenhouse gas in the lowest layers of the atmosphere is water vapour, which accounts for about 50% of the warming effect. The second largest contributor is carbon dioxide. Additionally, humans have released into the atmosphere large amounts of many gases of natural origin and many new, man-made greenhouse gases, such as halogenated hydrocarbons.

Greenhouse gas molecules are able to absorb heat radiation within certain wavelengths and re-radiate the heat out towards space, but some is re-radiated back towards the Earth, warming the surface and the lower atmosphere.

The Global Warming Potential Index (GWP) describes the relative warming potency of a greenhouse gas compared to carbon dioxide. A GWP reading depends on the atmospheric lifetime of the gas, the absorption of infrared radiation by a given type and the spectral location of its absorbing wavelengths. A GWP is calculated over a specific time interval. For example, nitric oxide has a warming potential of 298 over twenty years, whereas methane’s potential GWP is 72 and tetrafluoromethane’s is 4950 over twenty years. The major greenhouse gases based on GWP values in order from strongest to weakest are nitric oxide, methane and carbon dioxide. In addition, fluoride-based compounds (for instance, CFY tetrafluoromethane) are strong greenhouse gases, but their amount in the atmosphere is low. (IPCC, AR4, p 212)

The greenhouse effect can be observed by using the blackbody radiation model. A blackbody describes an idealized physical body that completely absorbs all incident rays, and does not reflect any. For example, the Sun and other stars can be modelled reasonably well as a blackbody and this helps to derivate their planetary equilibrium temperature.

The solar radiation intensity in the upper layers of the atmosphere varies depending on the distance from 1413 W/m2– 1321 W/m2. The Earth’s surface temperature depends on the energy balance between the energy the Earth receives from the Sun and energy it radiates back into outer space. The amount of energy the Earth absorbs from the Sun depends on the albedo that describes the reflectance of the surface. If the albedo is zero, a blackbody absorbs all incident radiation, and if it reflects all incident radiation, its scale is one. If we leave out the impact of the atmosphere, assuming the Earth is a blackbody and has an albedo value of 0,306, the Stefan-Boltzmann law then gives estimates of the Earth’s average surface temperature, -18°C. If we would assume the Earth absorbing all the incident radiation, the surface temperature would be 5,3°C. However, the average surface temperature on the Earth is much higher, at14°C. So the greenhouse effect increases the Earth’s temperature significantly.

Thermal radiation absorbed by the atmosphere depends on the wavelength of the radiation. The most important solar spectral irradiance variations are seen in infrared, visible light and ultraviolet wavelengths. The atmosphere has an ability to absorb infrared radiation. The warm Earth emits infrared radiation and the atmosphere absorbs radiation from the Earth’s surface. Atmospheric temperature is governed by the balance between heat energy absorbed by solar radiation and how much heat the Earth’s surface and atmosphere radiate back into space. The energy transfer between the Earth’s surface and atmosphere is based on phase changes and heat transfer Q=cm∆t.

Kevin Gill

Climate change has a major impact on global temperatures and precipitation. This chapter focuses on the immediate effects of the change in weather patterns, for example, the changing water cycle, storm intensity, sea level rise and decrease of snow and ice cover.

In addition to oceans, lakes and rivers, the Earth’s water is in the ground, in the atmosphere as water vapour and in plants and glaciers. Water is in constant movement between these, and climate change speeds up water cycles since atmospheric warming spurs the evaporation of water globally. Rainfall rates increase on average and the warmer atmosphere can then hold more water vapour.

Precipitation varies greatly from region to region. It has been estimated that rainfall will increase overall and changes in its distribution will increase resulting in ever greater and more frequent extreme weather events. In the future, heavy rains may occur in regions where the average precipitation does not increase. Similarly, droughts will last longer.

The main energy source of hurricanes is warm seawater. Their incidence and destructive potential are increasing due to the fact that seawaters are becoming warmer as a result of climate change. Seawater temperature is not the only factor in forecasting the intensity of tropic storms, but the warmer the seas, the more time the storms have to develop into hurricanes as they interact with meteorological factors in the atmosphere.

Currently, according to model-based climate change detection studies, storms will become stronger in the future, however it is not known when and where. In addition, it may come to pass that while the intensity of storms increase, their numbers globally decrease.

The amount of snow and ice are decreasing. Winters in the north and mountainous areas will be shorter and with less snow. It is more difficult to predict how quickly the remaining glaciers will melt, but it is estimated that the sea ice will be shrinking.

The Earth’s most important ice areas are currently the ice sheets of Antarctica, Greenland and the sea ice sheets of the polar regions. There are many differences between ice sheets and sea ice in volume and quality. According to our current knowledge, it is difficult to predict ice sheet behaviour. The volume of the Antarctica glaciers will remain more or less the same year after year since it accumulates the same mass of snow as it loses to the sea. This situation is expected to stay constant for the next few decades. However, in Greenland the climate is expected to become considerably warmer. Over the last fifteen years, Greenland’s ice loss has increased and the ice flow has become faster. The reason for the increased flow is not known, but it is believed that global warming could be one of the accelerating factors. If so, the ice sheets might melt faster than anyone has predicted.

According to the Archimedes’ principle, the melting of floating sea ice does not contribute to sea level rise. However, it accelerates global warming and therefore raises sea levels indirectly in the long run. Currently it seems likely that there will no longer be summer sea ice in the Arctic Sea in the future. In addition, it has been estimated that sea ice in the Southern Ocean will continue to decline over the next 100 years, however it is warming much slower than the northern seas.

United Nations Photo

The seawater level rises due to climate change for two main reasons: ice loss from glaciers increases the amount of melt water and, secondly, thermal expansion happens as water heats up and expands. Currently, the annual rate of the sea level rise is about 3 mm. This depends on, among other things, the rate of heat transfer from the deeper ocean by water currents. The future sea level is much harder to predict than global temperatures but depending on the many estimations and scenarios, it is predicted to rise between one and several meters in the 21st century.

The sea level rise varies from region to region around the planet. The rate of rise depends on the ocean currents, the salinity of seawater, temperature changes and the physical properties of oceanic crust. In addition, the distribution of glacier melt water varies greatly. Warm sea bodies are expected to be hit hardest by the impacts of thermal expansion.

The huge mass of water frozen in ice sheets exerts a powerful gravitational force that pulls on nearby seawater. When the mass is melting, the gravitation gets weaker and seawater escapes from the melting ice sheet. Therefore, according to climate model simulation results, melt water would not cause much sea level rise, for example, around the Baltic Sea; however the melting Antarctica glaciers would be more tangible.

Kevin Hale

The climate system consists of the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere that interact constantly with each other. The system is highly interdependent in that change in any one of them triggers responsive changes in some of the others. Usually, these changes either amplify or diminish the effects of the triggering event. This phenomenon is called climate change feedback.

The complexity of the climate system sets challenges for predicting future climate. Feedbacks make climate change a non-linear and unpredictable process. Feedbacks determine to what extent events that originally cause warming (climate forcing) change the Earth’s temperature.

Currently it is estimated that every radiative forcing watt per square meter would increase the Earth’s temperature approximately by around 0,75°C. However, according to some climate models, the change in temperature is about 0,5°C, whereas others estimate it being around 2°C. Increase in radiative forcing causes global warming over a 50 to 100 year timescale. The oceans decrease immediate temperature changes acting as heat buffers in the climate system.

It has been observed that over the last 100 years the temperature of the Earth has increased 0,7°C. According to a rough estimate, the positive radiative forcing of 1,6 watts which humans have produced so far would in theory warm the entire globe around 1,2°C in the long run. This estimate is not necessarily specific for two reasons:

1. Figuring out the actual value of radiative forcing is complicated and difficult.
2. Models of climate sensitivity and feedbacks vary greatly in their projections.

The following sums up the mechanisms of four different feedback loops:

• Water vapour amplifies global warming. A warm atmosphere can hold more water vapour. Since water vapour is a potent greenhouse gas, the increase in water vapour content decreases heat escaping from the Earth into space. Although the direct impacts of man-made emissions of water vapour are low, water vapour feedback tends to amplify global warming triggered by an increase in atmospheric CO2. It has been estimated that the water vapour feedback is capable of doubling the effect of warming caused by other sources..
• Snow and ice cover reflect solar energy back into space. When the globe gets warmer, snow and ice will melt and the amount of snow and ice cover on land will decrease. Dark soil or sea surface reflect much less sunlight than surfaces which are covered in snow or ice. Thus the surface absorbs more sunlight, which accelerates global warming. This feedback is not globally as important as the water vapour feedback, but it is crucial in the cold climate zones.
• Climate change leads to a change in clouds. Cloud feedback is complex, and so far climate models have not been able to provide reliable answers on how clouds respond to changes in the climate. In general, however, clouds cool the Earth’s surface. In a hypothetical cloudless Earth, sunlight would heat up the land without obstruction. It seems likely that climate change is changing the global distribution of clouds and in most of the models cloud feedback amplifies climate change, but different global climate models often give somewhat different results.
• The decline of carbon sinks increases global warming. When carbon dioxide is added to the atmosphere, the global carbon cycle divides the amount between the atmosphere, vegetation and oceans. It seems that in the future the land and oceans will be able to take up considerably less carbon dioxide than at present which would mean that carbon dioxide would remain mostly in the atmosphere warming the planet. Therefore, the decline of carbon capture and sequestration (carbon sinks) act as a feedback that amplifies climate change.

Typically feedback mechanisms work also the other way around. For example, if the climate becomes cooler for some reason, a decrease of water vapour in the atmosphere cools the climate even more and the amount of snow and ice increases and amplifies this cooling effect.

Humans accelerate global warming by adding greenhouse gases to the atmosphere, but on the other hand, we also produce atmospheric particulate emissions that cool the planet. The impacts of these contradictory phenomena can be demonstrated with the concept of climate change forcing through estimating its impact caused by different factors. Climate change forcing is measured by the rate of energy per unit area i.e. the rate of radiation force per square meter (W/m2).

Climate forcing describes the amount of energy the Earth receives from the Sun verses the amount of energy it radiates back into space. Sunlight has a positive forcing effect that warms the planet and its atmosphere. The Earth’s atmosphere and surface absorb a part of this radiation and the rest is reflected back into space. The Earth’s average temperature depends on the balance between heat energy absorbed and that which escapes the planet’s system, and human activities do cause changes in this energy balance. The Earth’s ability to absorb energy is reduced by cloudiness, reflectance of glaciers (albedo) and atmospheric particulate emissions, which reflect solar radiation back into space. About 30% of incoming solar energy is reflected back to space and 70% is absorbed by the Earth’s surface. In addition, climate forcing depends on changes in the reflectance of the ground’s surface, volcanic gases, the Earth’s orbit and atmospheric concentrations of greenhouse gases.

Human activities cause changes in climate forcing, i.e. the energy imbalance in the Earth’s climate system. The effect of the added greenhouse gases in the atmosphere reduces the amount of heat radiation reflected back into space and causes warming i.e. positive radiative forcing. In contrast, atmospheric particulate matter reduces the warming effect of solar radiation and thus causes cooling i.e. negative radiative forcing.

Particulates are microscopic solid or liquid matter suspended in the Earth’s atmosphere with a diameter of 100 micrometre to 100 nanometre. Human activities, such as burning fossil fuels in vehicles and coal combustion, generate significant amounts of particulates. Their sources can also be natural. Atmospheric particulate matter has mainly a cooling effect that slows the overall rate of global warming; however, they are short-lived and it is likely their amount will increase in the future, so their role as a climate cooler will become less significant. Particulates have the following types of cooling (C) and warming (W) effects on the atmosphere of the Earth:

• They are light-scatterers and reduce energy’s absorption by the surface (C).
• They increase cloudiness and diminish climate forcing (C).
• They absorb radiation and heat in the layers of the atmosphere carrying particulates (W).

The increase in water vapour greenhouse gases in the atmosphere and changes in the reflectance of soils, i.e. albedo due to land-use change amplifying the absorption of incoming solar radiation. Albedo decreases, for example, when a glacier melts or a field or clear-felled area becomes forested. Glaciers have a strong albedo, in other words, they reflect most of the radiation they come into contact with back into space. When a glacier melts, it reveals dry surfaces with a lower albedo, which increases absorption of solar radiation. Forest albedo is lower than in open areas and therefore forests contribute to global warming. Albedo weakens boreal forests as carbon sinks.

Human greenhouse gas increase has made climate scientists attempt to take action to tackle climate change through various interventions. In a nutshell, the concept of climate engineering is based on managing the Earth’s energy budget with different methods, which would either (D) deflect sunlight away from the Earth or (I) increase the amount of solar heat the Earth reflects back into space by removing carbon dioxide. Here are a few engineering proposals for removing CO2 from the atmosphere:

• Re-creating the effect of volcanic eruptions by pumping huge clouds of sulphur particles into the atmosphere (D).
• Increasing soils’ and clouds’ albedo (cloud brightening) (D).
• Use of space mirrors (D).
• Sequestrating carbon by fertilizing oceans to promote algae blooms (I).
• Producing biomass for charcoal like biochar and using it for agricultural purposes, which also aids in carbon sequestration (I).
• Creating so-called artificial trees that would capture and store CO2 through chemical and industrial processes (I).
• Modification of cirrus clouds (I).

Studies suggest that technical climate engineering could significantly reduce climate change if the technical hurdles can be overcome. Intervention on a large scale may possibly help to prevent a global temperature increase and the melting of polar ice caps. It could also help to reduce changes in precipitation extremes and prevent droughts and famine in some regions.

However, most experts advise against relying on climate engineering techniques as a simple solution to global warming instead of the imperative to cut greenhouse gas emissions. Climate interventions may be useful to mitigate catastrophic climate change while simultaneously carbon emissions are being reduced. An increase in the reflectivity of the atmosphere combined with ever-increasing greenhouse gas emissions may run a great risk of disrupting natural systems. Large-scale interventions also have a potential for huge, unpredictable negative consequences, such as these:

• Even if the scientific basis for climate engineering would be sufficiently clear, the interventions may involve regional climate disruptions due to solar radiation management.
• Pumping and spraying sulphate into the stratosphere would increase the ozone hole and causing damaging ultraviolet radiation to reach the Earth’s surface.
• In some regions, precipitation could be delayed or inhibited unexpectedly. For example, in the Amazon rainforest rainfall may be significantly reduced and the Asian monsoons might weaken, which would cause food and water shortage for billions of people.
• In the case of interrupted climate engineering, the Earth’s temperature may rapidly increase. A sudden climate change would potentially put many ecosystems at risk and pose a huge challenge for human adaptation.

Fossil fuels have formed by natural processes when microorganisms have broken down plankton and other biodegradable material in the absence of oxygen under water millions of years ago. Over thousands of years, this organic matter, mixed with mud, got buried under heavy layers of sediment. The resulting high levels of heat and pressure caused the organic matter to chemically alter.

Currently oil (31,4%), coal (29%) and natural gas (21,3%) account for more than 80% of global primary energy consumption. Fossil fuels consist of a mixture of various hydrocarbons and the specific mix gives fuels their characteristic properties, such as their boiling point and density. Since fossil fuels are formed in natural processes from organic matter, they all contain high percentages of carbon. As it is the case with other organic compounds when burnt (oxidizing), the carbon and hydrogen atoms combine with oxygen atoms to produce carbon dioxide and water vapour. Combustion also releases chemical energy, which is transferred to the surroundings as thermal energy and light. Our energy production system is currently widely based on this mechanism.

After the Industrial Revolution, world energy use increased more than ten times in the 20th century from 911 million tonnes of oil to 9645 million tonnes as the world’s population increased from 1 billion to 6 billion. Today coal, oil and natural gas are the most important non-renewable energy sources. Compared to these, the share of nuclear energy usage is relatively small. Renewable energy technologies are constantly under development around the world, and recently wind and solar power, geothermal energy, and hydroelectricity technologies have improved significantly.

Fossil fuels and industrial energy generation have increased industrial production and improved our wellbeing and living standards. Cheaper goods and services are being produced rapidly in ever-increasing amounts and transported to consumers over long distances. Consumer goods are affordable to more and more people, and aggressive marketing creates an artificial need to consume more. Subsequently, our lifestyle based on burning fossil fuels has created global problems, such as climate change.

cypheroz

Burning fossil fuels generates greenhouse gases, and non-renewable energy sources will eventually be exhausted. In order to make energy production sustainable, it has to be based on renewable sources. Current renewable energy sources are primarily based on the sun’s energy. Hydropower requires water evaporating from the oceans and then depositing it on land with wind. The energy in wind also comes from the Sun. Burning wood, cardboard or biodiesel releases solar energy that plants and other organisms have absorbed in photosynthesis. The only non-solar based renewable energy forms are tidal power and geothermal energy.

The following chapters introduce different energy sources. Their use is being examined in the current context as represented by what is happening in Finland. Find out about the situation in your country.

In Finland, hydropower is the most important renewable energy source in electricity generation. In the 1960’s, 90% of the country’s electricity was generated by hydropower; however, currently it accounts for merely between 10 and 15% of the country’s total energy consumption. The principle of hydropower generation is very simple: flowing water rotates turbine blades, which rotate electric generators.

Hydropower is a reliable, renewable, clean and local energy source. However, it also has various disadvantages, such as the need to construct dams and spillways which are harmful for some aquatic ecosystems. In addition, hydropower availability varies greatly from year to year. It is dependant on rainfall, and rivers normally have their lowest flow during winter, precisely when energy demand is at its highest. In Finland, most rivers with hydropower potential already have dams in place and therefore, capacity cannot be increased by much.

Biomass originates through plants absorbing the Sun’s energy in a process called photosynthesis. It can be burned by thermal conversion. In Finland, bioenergy sources contribute 20% of the national energy consumption including wood, forest industry black liquor, household waste, landfill gas, biodiesel from vegetable oils, and ethanol from sugar. This means that forests in Finland provide new business opportunities for bioenergy production.

Biofuels are renewable and often carbon neutral. In addition, their production creates jobs in the energy sector and improves a country’s self-sufficiency. However, large-scale replacement of fossil fuels with wood could create a number of problems since it would mean more logging and a decrease in the forests’ sink effectiveness. In countries that suffer from an acute shortage of food, a demand for crops for biofuel production could amplify the hunger condition. In Finland, use of field-grown grass and manure as a raw material for biogas reactors could bring many energy, nutrient cycle and climate benefits. Currently, many biofuels are exported and their generation can be harmful for the environment.

Wind power is achieved by converting the kinetic energy in wind into electricity, usually by using a large wind turbine consisting of propellers. In 2016, wind power amounted to around 4% of the country’s electricity production. There is plenty more potential since Finland’s coasts, maritime areas and mountains are ideal for increasing wind power capacity. With advanced wind power technologies, the interior of the country is also suitable for wind power plants. Wind farms are growing in number around the world. It is estimated that a wind turbine will pay back the energy needed to build, install, maintain and dismantle it within about three to nine months. Wind power plants are simple, reliable and relatively affordable. Component manufacturing for wind farms, their construction, use and maintenance create new jobs in Finland. Wind power generation is directly linked to weather conditions, but it can be forecasted according to electricity market requirements. Well thought out modelling and design helps to minimize the negative impacts on the landscape, ecosystems and species, such as birds. There have been some complaints about wind turbine noise, but studies have not found evidence that wind farms would cause health problems.

Solar power is defined as the conversion of energy from sunlight into electricity or heat energy. The process of harnessing solar energy normally refers to the use of photovoltaics i.e. solar panels or solar cells. Indirect forms of solar energy are hydropower, wind power, tidal power and bioenergy. Globally, solar power is the fastest-growing renewable energy source. In Finland, solar power has a great deal of untapped potential, particularly in the areas without access to electricity. Today, many combine intermittent energy sources with solar panels or cells.

Geothermal energy is a functional energy source for heating single-family houses. It is harvested by capturing heat absorbed at the Earth’s surface from solar energy. Energy is captured on the surface through a borehole heat collector after which a heat pump transfers the energy into potable water for use by homes and industries. A heat pump can be thought of as a heat engine which is operating in reverse; it moves heat from ground pipes at a lower temperature to potable water at a higher temperature. The re-chilled fluid is then sent back into the ground continuing the circle. Geothermal heating is an environmentally friendly heating and cooling system. The major disadvantage of a geothermal heat pump is the high initial cost.

The growth in the Finnish Lämpöpumput heat pump market has been so rapid and great that the amount of energy these pumps generate annually is equivalent to that of one Loviisa (a city in Finland) nuclear power plant unit. Heat pumps are designed to move thermal energy from the ground, water, outside air or outgoing air to water or indoor air. They perform similar functions to the refrigerator, which absorbs the heat from the freezer and then puts it into the atmosphere, which is at a higher temperature. One of the benefits of ground source heat pumps is that generating energy using it is affordable and helps to reduce energy bills significantly.

Nuclear power is an exception among the low-emission energy sources since it is made with uranium, a chemical element found in nature, which is not a renewable source. Heat is produced from the energy released when splitting atoms in nuclear fission. The fission process releases a great deal of energy, so nuclear fuels produce significantly more energy than other fuels. According to the IPCC, nuclear power is a low-carbon and stabilized energy source, but its share of global electricity generation has been declining due to operational risks and the associated safety concerns, such as unsolved waste management issues and nuclear weapon proliferation concerns.

jmoran24