Ozone Layer

The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation. It contains high concentrations of ozone (O₃) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 20 to 30 kilometres (12 to 19 mi) above Earth, although the thickness varies seasonally and geographically. 

The ozone layer was discovered in 1913 by French physicists Charles Fabry and Henri Buisson. Measurements of the sun showed that the radiation sent out from its surface and reaching the ground on Earth is usually consistent with the spectrum of a black body with a temperature in the range of 5,500-6,000 k (Kelvin) (5,227 to 5,727°C), except that there was no radiation below a wavelength of about 310 nm at the ultraviolet end of the spectrum. It was deduced that the missing radiation was being absorbed by something in the atmosphere. Eventually the spectrum of the missing radiation was matched to only one known chemical, ozone. Its properties were explored in detail by the British meteorologist G.M.B Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958, Dobson established a worldwide network of ozone monitoring stations, which continue to operate to this day. The "Dobson unit", a convenient measure of the amount of ozone overhead, is named in this honor.

The United Nations General Assembly has designated September 16 as the International Day of the Preservation of the Ozone Layer. 

Venus also has a thin ozone layer at an altitude of 100 kilometers from the planet's surface.

Ultraviolet light

Although the concentration of the ozone in the ozone layer is very small, it is vitally important to life because it absorbs biologically harmful ultraviolet (UV) radiation coming from the sun. Extremely short or vacuum UV (10–100 nm) is screened out by nitrogen. UV radiation capable of penetrating nitrogen is divided into three categories, based on its wavelength; these are referred to as UV-A (400–315 nm), UV-B (315–280 nm), and UV-C (280–100 nm) .

UV-C, which is very harmful to all living things, is entirely screened out by a combination of dioxygen (< 200 nm) and ozone  (> about 200 nm) by around 35 kilometres (115,000 ft) altitude. UV-B radiation can be harmful to the skin and is the main cause of sunbury; excessive exposure can also cause cataracts, immune system suppression, and genetic damage, resulting in problems such as skin cancer. The ozone layer (which absorbs from about 200 nm to 310 nm with a maximal absorption at about 250 nm) is very effective at screening out UV-B; for radiation with a wavelength of 290 nm, the intensity at the top of the atmosphere is 350 million times stronger than at the Earth's surface. Nevertheless, some UV-B, particularly at its longest wavelengths, reaches the surface, and is important for the skin's production of vitamin D.

Ozone is transparent to most UV-A, so most of the longer-wavelength UV radiation reaches the surface, and it constitutes most of the UV reaching the Earth. This type of UV radiation is significantly less harmful to DNA, although it may still potentially cause physical damage, premature aging of the skin, indirect genetic damage, and skin cancer.

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Greenhouse Effect

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.

If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) the atmosphere will radiate energy in all directions. Part of this radiation is directed towards the surface, warming it. The downward component of this radiation-that is, the strength of the greenhouse effect-will depend on the atmosphere's temperature and on the amount of greenhouse gases that the atmosphere contains.

On Earth, the atmosphere is warmed by absorption of infrared thermal radiation from the underlying surface, absorption of shorter wavelength radiant energy from the sun, and convective heat fluxes from the surface. Greenhouse gases in the atmosphere radiate energy, some of which is directed to the surface and lower atmosphere. The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.

Earth's natural greenhouse effect is critical to supporting life. Human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming. 

The mechanism is named after a faulty analogy with the effect of solar radiation passing through glass and warming a greenhouse. The way a greenhouse retains heat is fundamentally different, as a greenhouse works by reducing airflow and retaining warm air inside the structure. 

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Greenhouse Gas

A Greenhouse gas is a gas in an atmosphere that absorbs and emits radiation with the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about−18 °C (0 °F), rather than present average 15 °C (59 °F) . In the Solar System, the atmospheres of Venus, Mars and Titan also contain gases that cause a greenhouse effect. 

Human activities since the beginning of the Industrial Revolution (taken as the year 1750) have produced a 40% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 400 ppm in 2015. This increase has occurred despite the uptake of a large portion of the emissions by various natural "sinks" involved in the carbon cycle. Anthropogenic carbon dioxide (CO₂) (i.e. emissions produced by human activities) emissions come from combustion of carbon-based fuels, principally coal, oil, and natural gas, along with deforestation, soil erosion and animal agriculture.

It has been estimated that if greenhouse gas emissions continue at the present rate, Earth's surface temperature could exceed historical values as early as 2047, with potentially harmful effects on ecosystems, biodiversity and the livelihoods of people worldwide. Recent estimates suggest that on the current emissions trajectory the earth could pass a threshold of 2°C global warming, which the United Nations' IPCC designated as the upper limit for "dangerous" global warming, by 2036.

Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth. In order, the most abundant green house gases in Earth's atmosphere are:

• Water vapor (H
  2O)
• Carbon dioxide (CO₂)
• Methane (CH
  4)
• Nitrous oxide (N
  2O)
• Ozone (O
  3)
• Chlorofluorocarbons (CFCs)

Atmospheric concentrations of greenhouse gases are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound). The proportion of an emission remaining in the atmosphere after a specified time is the "airborne fraction" (AF). More precisely, the annual airborne fraction is the ratio of the atmospheric increase in a given year to that year's total emissions. Over that last 50 years (1956–2006) the airborne fraction for CO₂ has been increasing at 0.25 ± 0.21%/year.

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Solutions to Global Warming

Solutions to Global Warming

There is no single solution to global warming, which is primarily a problem of too much heat-trapping carbon dioxide, methane and nitrous oxide in the atmosphere. (Learn more about the causes of global warming.)The technologies and approaches outline below are all needed to bring down the emissions of these gases by at least 80% by mid-century. To see how they are best deployed in each region of the world, use the menu at left

1. Boosting energy efficiency: The energy used to power, heat, and cool our home, businesses, and industries is the single largest contributor to global warming. Energy efficiency technologies allow us to use less energy to get the same or higher-level of production, service, and comfort. This approach has vast potential to save both energy and money, and can be deployed quickly.

2. Greening transportation: The transportation sector's emissions have increased at a faster rate than any other energy-using sector over the past decade. A variety of solutions are at hand, including improving efficiency (miles per gallon) in all modes of transport, switching to low-carbon fuels, and reducing vehicle miles travels through smart growth and more efficient mass transportation systems.

3.  Revving up renewables: Renewable energy sources such as solar, wind, geothermal and bio energy are available around the world. Multiple studies have shown that renewable energy has the technical potential to meet the vast majority of our energy needs. Renewable technologies can be deployed quickly, are increasingly cost-effective, and created jobs while reducing pollution. 

4. Phasing out fossil fuel electricity: Dramatically reducing our use of fossil fuels, especially carbon intensive coal-is essential to tackle climate change. There are many ways to begin this process. Key action steps including: not building any new coal-burning power plants, initiating a phased shutdown of coal plants starting with oldest and dirties, and capturing and storing carbon emissions from power plants. While it may sound like science fiction, the technology exists to store carbon emissions underground. The technology has not been deployed on a large scale or proven to be safe and permanent, but it has been demonstrated in other contexts such as oil and natural gas recovery. Demonstration projects to test the viability and costs of this technology for power plant emissions are worth pursuing.

5. Managing forests and agriculture: Taken together, tropical deforestation and emissions from agriculture represent nearly 30% of the world's heat-trapping emissions. We can fight global warming by reducing emissions from deforestation and forest degradation and by making our food production practices more sustainable. 

6. Exploring nuclear: Because nuclear power results in few global warming emissions, an increased share of nuclear power in the energy mix could help reduce global warming, but nuclear technology poses serious threats to our security and, as the accident at the Fukushima Diaichi plant in Japan illustrates to our health and the environment as well. The question remains: can the safety, proliferation, waste disposal, and cost barrier of nuclear power be over come?

7. Developing and deploying new low-carbon and zero-carbon technologies: Research into and development of the next generation of low-carbon technologies will be critical to deep mid-century reductions in global emissions. Current research on battery technology, new materials for solar cells, harnessing energy from novel sources like bacteria and algae, and other innovative areas could provide important breakthroughs.

8.  Ensuring sustainable development: The countries of the world-from the most to the least developed, vary dramatically in their contributions to the problems of climate change and in their responsibilities and capacities to confront it . A successful global compact on climate change must include financial assistance from richer countries to poorer countries to help make the transition to low-carbon development pathways and to help adapt to the impacts of climate change. 

Finally the impacts of a warming world are already being felt by people around the globe. If climate change continues unchecked, these impacts are almost certain to get worse. From sea level risen to heat waves, from extreme weather to disease outbreaks, each unique challenge requires locally-suitable solutions to prepare for and respond to the impacts of global warming. Unfortunately, those who will be hit hardest and first by the impacts of a changing climate are likely to be the poor and vulnerable , especially those in the least developed countries. Developed countries must take a leadership role in providing financial and technical help for adaption.

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Global Warming

Global warming and climate change are terms for the observed century-scale rise in the average temperature of the Earth's climate system and its related effects. Multiple lines of scientific evidence show that the climate system is warming. Although the increase of near-surface atmospheric temperature is the measure of global warming often reported in the popular press, most of the additional energy stored in the climate system since 1970 has gone into the oceans. The rest has melted ice and warmed the continents and atmosphere. Many of the observed changes since the 1950s are unprecedented over tens to thousands of years. 

Scientific understanding of global warming is increasing. The Intergovernmental Panel on Climate Change (IPCC)reported in 2014  that scientists were more than 95% certain that global warming is mostly being caused by human (anthropogenic) activities , mainly increasing concentrations of greenhouse gases such as carbon dioxide  (CO₂) . Human-mad carbon dioxide continues to increase above levels not seen in hundreds of thousands of years. Currently, about half of the carbon dioxide released from the burning of fossil fuels remains in the atmosphere. The rest is absorbed by vegetation and the oceans. Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 °C (0.5 to 3.1 °F)  for their lowest emissions scenario and 2.6 to 4.8 °C (4.7 to 8.6 °F) for the highest emissions scenario. These findings have been recognized by the national science academies of the major industrialized nations. and are not disputed by any scientific body of national or international standing.

Future climate change and associated impacts will differ from  region to region around the globe.

Anticipated effects include warming global temperature, rising sea levels, changing precipitation, and expansion of deserts in the subtropics. Warming is expected to be greater over land than over the oceans and  greatest in the Arctic, with the continuing retreat of glaciers, permafrost and sea ice. Other likely changes include more frequent extreme weather events including heat waves, droughts, heavy rainfall  with floods  and heavy snowfall; ocean acidification; and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels. Because the climate system has a large "inertia" and CO₂ will stay in the atmosphere for a long time, many of these effects will not only exist for decades or centuries, but will persist for tens of thousands of years.

Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, building systems resilient to its effects, and possible future climate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change (UNFCCC), whose ultimate objective is to  prevent dangerous anthropogenic climate change. Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below  2.0 °C (3.6 °F) relative to pre-industrial levels, with efforts mad to limit warming to 1.5 °C (2.7 °F).

Public reactions to global warming and concern about its effects are also increasing. A global 2015 Pew Research Center report showed a median of 54% consider it "a very serious problem". There are significant regional differences, with Americans and Chinese (whose economies are responsible for the greatest annual CO2 emissions) among the least concerned.

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Impacts of Climate Change in Canada

Over the period 1948 to 2013, the average annual temperature in Canada has warmed by 1.6 °C (relative to the 1961-1990 average), a higher rate of warming than in most other regions of the world. Increased winter and spring temperatures have contributed to this warming trend to a greater degree than other seasons. Warming trends are seen consistently across Canada, but regions showing the strongest warming trends are found in the far north.

Strong warming in high-latitude regions is a robust characteristic of projections of future climate change as well. This indicates that the climate of Canada, particularly in the North, to which Canadians have been accustomed and to which we have adapted our activities, is expected to undergo substantial change in the future.

Future warming will be accompanied by other changes, including the amount and distribution of rain, snow, and ice and the risk of extreme weather events such as heat waves, heavy rainfalls and related flooding, dry spells and/or droughts, and forest fires. In addition, Canada is a maritime nation with 8 to its 10 provinces and all three territories bordering on ocean waters. Thus many regions of Canada will also be affected by changing ocean environments, including changes in average and extreme sea level, wave regimes, and ice conditions. Dramatic reductions in Arctic sea ice cover, particularly during the summer season, are already evident and well documented, and have been attributed to human-induced global warming.

Canada in a Changing Climate: Sector Perspectives on Impacts and Adaptation is an update to the 2008 report, From Impacts to Adaptation: Canada in a Changing Climate. The report assesses literature published since 2007 on climate change impacts, adaptation and vulnerability in Canada. It includes chapters on natural resources, food production, industry, biodiversity and protected areas, human health, and water and transportation infrastructure.

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How to eliminate climate change

Top 10 things to eliminate climate change

1. Reduce energy use

Adopt energy-saving habits. Make it a habit to turn off the lights as you leave a room. Also, replace standard light bubs with energy-efficient compact fluorescent bulbs. Turn of your computer and unplug electronics when they are not in use.

2. Change the way you think about transportation

Walk or bike whenever possible. Not only will you reduce your carbon footprint, but your overall level of health will improve and you will save money on parking and gasoline. Take public transit or carpool whenever possible. When purchasing a vehicle look for one with better mileage. Increase your fuel economy when driving by sticking to posted speed limits and avoiding rapid acceleration and excessive braking. Plan and combine trips and errands. This will save you both time and money as well as reduce wear and tear on your vehicle. When travelling long distances, try to take a train or bust rather than flying or driving. 

3. Insulate your home

Insulate yourself and your home. By properly insulation your home, you can ensure that heat stays in or out depending on the season. You can do this by purchasing windows and window coverings that will block out or keep in warmth, and by sealing any existing cracks. In winter, reduce your thermostat by 2 °C to enjoy energy savings and a cozy sweater. In summer, use fans to circulate air, and set air conditioners to make your home a comfortable temperature. Lowering the temperature on your water heater to between 55 and 60 °C  and insulting your pipes also makes a difference.

4. Make every drop count

Conserve water by fixing drips and leaks, and by installing low-flow shower heads and toilets. Challenge yourself to a speed shower. Turn off water while brushing teeth or shaving. Treating and transporting water requires energy, while water conservation results in reduced energy requirements and carbon emissions. 

5. Cool wash and hang to dry

These are not just washing instructions on a label anymore, but an equation for energy savings. Wash clothing in cold water and hang clothing to dry outside, or indoors on a drying rack. Taking these steps will reduce your electricity bill and also prolong the life of clothing by reducing wear on the fabric caused by by dryers.

6. High efficiency appliances

When replacing appliances, look for high efficiency units. Appliances with ENERGY STAR ratings,

an international standard for energy-efficient consumer products, typically utilize a minimum 20 %of less energy. This means savings for you and the environment.

7. Switch to "green power"

Research where your power is coming from-wind, water, coal, or solar-and talk to your power provider to determine if a greater percentage could be coming from renewable resources. Encourage power providers to switch to green power and, if possible and/or economically viable, switch to a company offering power from renewable resources.

8. Recycle

Make recycling part of your daily routine. Recycle all packaging and consumer goods that you can. Aim to purchase items with minimal and recyclable packaging. For certain items with a large amounts of packaging, ask retailers if they can recycle or reuse it. For electronics, facilities now exist that can dispose of electronics in an environmentally responsible manner. 

9. Repurpose

Rather than discarding or recycling clothing and household goods, give them a chance at a second life. Gently used clothing can be donated to charity or exchanged with friends and family. Old T-shirts can be repurposed into rags for cleaning. Household goods can be donated to charity or sold at a garage sale. Through repurposing, the amount of waste being set to landfill site is reduced, there is not need to use energy for recycling, and others can benefit from your used items.

10. Plants, our new best friend

When gardening, select plants that are well suited to your climate and require minimal watering and attention. Better yet, plant a tree, and it will provide shade and soak up carbon from the atmosphere.

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