Climate change is the result of greenhouse gases (GHGs), principally carbon dioxide, building up in our atmosphere and helping to trap heat. According to the vast majority of the world's scientists this has caused the climate to change globally.
Over the past two decades, the evidence that GHG is continuing to build-up as a result of human activities has become conclusive i.e. these changes have come about as a combined effect of increases in emissions, such as fossil fuel burning, and decrease in carbon sinks, such as reduced forest cover.
The Intergovernmental Panel on Climate Change (IPCC) is the leading international scientific body for the assessment of climate change. Thousands of scientists from all over the world contribute to the work of the IPCC on a voluntary basis.
The Working Group Summary was published in February 2007 and assesses the current scientific knowledge of the natural and human drivers of climate change, observed changes in climate, the ability of science to attribute changes to different causes, and projections for future climate change.
The report was produced by 620 authors and editors from 40 countries, and reviewed by more than 620 experts and 113 governments.
"Warming of the climate system is unequivocal."
"Most of the observed increase in global average temperatures since the mid-20th century is very likely i.e. over 90% likely, due to the observed increase in anthropogenic greenhouse gas concentrations."
Carbon dioxide, methane, and nitrous oxide are all long-lived greenhouse gases.
Carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values.
The amount of carbon dioxide in the atmosphere in 2005 (379 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm).
The amount of methane in the atmosphere in 2005 (1774 ppb) exceeds by far the natural range of the last 650,000 years (320 to 790 ppb).
The primary source of the increase in carbon dioxide is fossil fuel use, but land-use changes also make a contribution
The primary source of the increase in methane is very likely to be a combination of human agricultural activities and fossil fuel use. How much each contributes is not well determined.
Nitrous oxide concentrations have risen from a pre-industrial value of 270 ppb to a 2005 value of 319 ppb. More than a third of this rise is due to human activity, primarily agriculture.
Cold days, cold nights, and frost events have become less frequent. Hot days, hot nights, and heat waves have become more frequent.
Additionally, eleven of the twelve years in the period (1995â€“2006) rank among the top 12 warmest years in the instrumental record (since 1850, towards the end of the Little Ice Age).
Warming in the last 100 years has caused about a 0.74 Â°C increase in global average temperature. This is up from the 0.6 Â°C increase in the 100 years prior to the Third Assessment Report.
Observations since 1961 show that the ocean has been absorbing more than 80% of the heat added to the climate system, and that ocean temperatures have increased to depths of at least 3000 m (9800 ft).
Average Arctic temperatures increased at almost twice the global average rate in the past 100 years.
Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years (including both the Medieval Warm Period and the Little Ice Age).
Try these 10 ways to reduce your carbon footprint today.
Ever wonder how your tiny carbon footprint really impacts the big picture of climate change? Though you might feel like your lifestyle is insignificant compared to things like oil extraction or vehicle emissions, the choices we make in our day-to-day life â€” how we get around, what we eat, how we live â€” play a major role in slowing climate change.
Here's a list of 10 ways you can join in the fight to reduce our carbon footprint. Whether you save it on your desktop, share it with friends, or stick a copy on your fridge (PDF), this quick reference guide breaks down what you can do today to protect the planet for future generations.
Transportation causes about 25 per cent of Canada's greenhouse gas emissions, so walk, cycle or take transit whenever you can. You'll save money and get into better shape! If you can't go car-free, try carpooling or car sharing, and use the smallest, most fuel-efficient vehicle possible.
You already switch off lights â€” what's next? Change light bulbs to compact fluorescents or LEDs. Unplug computers, TVs and other electronics when not in use. Wash clothes in cold or warm (not hot) water. Dryers are energy hogs, so hang dry when you can. Install a programmable thermostat. Look for the Energy StarÂ® label when buying new appliances. And a home energy audit is cheaper than you think â€” book one today to find even more ways to save energy.
Ask your utility to switch your account to clean, renewable power, such as from wind farms. If it doesn't offer this option yet, ask it to.
Buy organic and locally grown foods. Avoid processed items. Grow some of your own food. And eat low on the food chain â€” at least one meat-free meal a day â€” since 18 per cent of greenhouse gas emissions come from meat and dairy production. Food writer Michael Pollan sums it up best: "Eat food. Not too much. Mostly plants."
Garbage buried in landfills produces methane, a potent greenhouse gas. Keep stuff out of landfills by composting kitchen scraps and garden trimmings, and recycling paper, plastic, metal and glass. Let store managers and manufacturers know you want products with minimal or recyclable packaging.
Carbon taxes make polluting activities more expensive and green solutions more affordable, allowing energy-efficient businesses and households to save money. They are one of the most effective ways to reduce Canada's climate impact. If your province doesn't have a carbon tax, ask your premier and to implement one.
Air travel leaves behind a huge carbon footprint. Before you book your next airline ticket, consider greener options such as buses or trains, or try vacationing closer to home. You can also stay in touch with people by videoconferencing, which saves time as well as travel and accommodation costs.
Follow the latest news about climate change. Join our communityHost a presentation for your community or workplace by requesting a presenter trained by Al Gore from The Climate Project Canada.
Take a few minutes to contact your political representatives and the media to tell them you want immediate action on climate change. Remind them that reducing greenhouse gas emissions will also build healthier communities, spur economic innovation and create new jobs. And next time you're at the polls, vote for politicians who support effective climate policies.