Climate Change - Chapter 1

Climate 

The slowly varying aspects of the atmosphere - hydrosphere - land surface system. It is typically characterized in terms of suitable averages of the climate system over periods of a month or more taking into consideration the variability in time of these averaged quantities 

Weather

The state of the atmosphere…As distinguished from climate, weather consists of the short term (minutes to days) variation in the atmosphere 

Why do we care about weather and climate? 

• Weather is important for making short term decisions. (i.e., do i need an umbrella) 

• Climate is important for long-term decisions. (i.e., if you are looking to buy a vacation home you are interested in funding a place that frequently has pleasant weather) 

Temperature

• Temperature is the parameter that is most often associated with climate and it is something that directly affects the well-being of the Earth’s inhabitants. 

  • The statistic that most frequently gets discussed is average temperature, but temperature extremes also matter. 

    • Heat-related mortality is the leading cause of weather-related death in the United States, killing many more people than cold temperatures do. 

Precipitation

• Precipitation rivals temperature in its importance to humans, because human life without fresh water is impossible. As a result, precipitation is almost always included in any definition of climate 

  • Total annual precipitation is obviously an important part of the climate of a region. However, the distribution of this rainfall throughout the year also matters. 

  • Other aspects of precipitation such as its form (rain vs snow), are also important. 

(e.g., In the US Pacific Northwest, for example, snow accumulates in the mountains during the winter and then melts during the following summer, thereby providing fresh water to the environment during the rain free summers. If warming causes wintertime precipitation to fall as rain rather than snow, then it will run off immediately and not be available during the following summer. This could lead to water shortages during the summer.)

Seasonal Climate Change

The climate change that is most familiar is the seasonal cycle: the progression of seasons from summer to fall to winter to spring and back to summer, during which most nontropical locations experience significant climate variations. 

Climate Change

Any systematic change in the long-term statistics of climate elements (such as temperature, pressure or winds) sustained over several decades or longer

Equator

The line of the Earth’s surface that is halfway between the North and South poles, and it divides the earth into a northern hemisphere and a southern hemisphere.

Latitude

The latitude of a particular location is the distance in the north-south direction between the location and the equator measure in degrees

Tropics

The tropics are conventionally defined as the region from 30 degrees north to 30 degrees south, and this region covers half the surface area of the planet

Mid Latitudes

The mid latitudes are usually defined as the region from 30 degrees to 60 degrees in both hemispheres, they occupy roughly one third of the surface area of the planet 

Human Populations in the Northern and Southern Hemispheres

Most human populations live in the northern hemisphere, between the equator and 60 degrees north because that's where most of the land is. The southern hemisphere is mainly ocean. 

Polar Regions

The polar regions are typically defined to be from 60 degrees to the pole, and together these regions occupy the remaining one-sixth of the surface area of the planet. 

Longitude

Longitude is the angle in the east or west direction, from the primer meridian, a line that runs from the North Pole to the South Pole, through Greenwich, England. 

Latitude and Longitude

Together, latitude and longitude identify the location of every point on the planet Earth. 

Scientific Method

• Science begins with the scientific method. It describes a process whereby an individual scientist generates a hypothesis, performs experiments to test the hypothesis and then reaches a conclusion about the hypothesis. 

• In reality this is only the first step of the true scientific process. Before the conclusions can be considered true it must be judged valid by the rest of the scientific community. 

• Scientific journals will not publish the paper until it has been critically reviewed by other experts in the field 

Scientific Consensus

Over time as the peer-reviewed literature fills up with replication and other tests of a claim, some claims become well-verified enough that they come to be regarded simply as scientific truth. When this happens we say that a scientific consensus on that claim has emerged

Scientific Assessments

• Scientific assessments are reliable summaries of peer-reviewed literature that is understandable to non-experts  

• Assessments start with policymakers defining the questions they want answered. Then, a writing team with relevant scientific expertise is assembled. After the writing team produces its assessment, the assessment is then itself peer reviewed by other experts in the field

• The most important assessments for climate science come from the Intergovernmental Panel of Climate Change (IPCC)