Global Environmental Change class content (Unit 1)

The Intergovernmental Panel on Climate Change (IPCC) defines climate as follows

“the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind.”

Building on intergovernmental panel definition, climate change is:

“a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer.

Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use.”

Building on intergovernmental panel definition, climate change is:

Weather is the state of the

air, temperature, and atmosphere in a given place at a specific moment in time.

Climate, as the definition above states, is a

statistical description of mean and variability in surface variables, like temperature and wind, over a period of time.

The definition of climate change reminds us that climate is not

constant; changes can, and do, happen over time and are driven by internal processes or external forcings.

At the end of August, Southern Ontario is almost always humid and very hot.

This is an example of Climate

It is 30 degrees Celsius today with high humidity

This is an example of weather

What is the green house effect

Sunlight reaches the Earth. Some energy is reflected back into space. Some energy is absorbed and re-radiated as heat. Most of the heat is absorbed by greenhouse gases and then radiated in all directions, warming the Earth

Green house gases absorb

solar radiation and re-radiate heat, which is a process central to the greenhouse effect

carbon dioxide (CO₂) is the

Dominant green house gas

Carbon dioxide is widely reported as the most

important anthropogenic greenhouse gas because it currently accounts for the greatest portion of the warming associated with human activities.

Carbon dioxide occurs naturally as

part of the global carbon cycle,

Even though Carbon Dioxide occurs naturally, human activity has

increased atmospheric loadings through combustion of fossil fuels and other emissions sources.

Natural sinks that remove carbon dioxide from the atmosphere (e.g., oceans, plants) help regulate

carbon dioxide concentrations,

Regarding natural sinks,

human activities can disturb these processes (e.g., deforestation) or enhance them.

Methane comes from many sources, including

human activity

What form of human activity can be the source of methane

Coal mining, natural gas production and distribution, waste decomposition in landfills, and digestive processes in livestock and agriculture

What are the natural sources of Methane

wetlands and termite mounds

Nitrous oxide is emitted during

agricultural and industrial activities

Other ways in which Nitrous oxide is emitted include

combustion of solid waste and fossil fuels.

Various synthetic chemicals, such as hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and other synthetic gases, are released as a result of

commercial, industrial, or household uses.

Many other gases are known to trap heat in the atmosphere. Examples include

Water Vapour and Ozone

Water Vapour Naturally

occurs as part of the global water cycle,

Ozone occurs

naturally in the stratosphere and is found in the troposphere largely due to human activities.

Humans are responsible for releasing

larger and larger volumes of greenhouse gas, especially CO₂, since the onset of the industrial revolution

The vast bulk of CO₂ emissions has been driven by

fossil- fuel burning, including steel production, and the wide petrochemical industry

In terms of emissions per year over the last decade or so, coal is the

main culprit, with oil at almost similar levels, and gas a distant third.

The Intergovernmental Panel on Climate Change (IPCC) identifies global warming as

an increase in combined surface air and sea surface temperatures averaged over the globe and over a 30-year period

In 2018, the IPCC released a report that made some predictions about the likelihood of keeping average global warming to 1.5°C or less (relative to pre-industrial levels). The report summarizes:

Most land regions are experiencing greater warming than the global average, while most ocean regions are warming at a slower rate. Depending on the temperature dataset considered, 20–40% of the global human population live in regions that, by the decade 2006–2015, had already experienced warming of more than 1.5°C above pre-industrial in at least one season

Science strongly suggests that human emissions of greenhouse gases since

the industrial revolution are driving climate change and that global warming is a key indicator of that change.

Climate change is a key (but not only!) human impact on the

Environment

Global warming is a key (but not only!) outcome of

Climate Change