Global Climate Change

You Must Know Earth’s climate system and the many factors influencing global climate (see ClimateReview.ppt) How humans influence Earth’s atmosphere and climate The current and future trends and impacts of global climate change. Specific responses and actions we can take to climate change. The economic considerations and approaches involved in the reduction of greenhouse gas emissions.

What is Climate Climate is the aggregated patter of weather, meaning averages, extremes, timing, spatial distribution of… temperatures hot & cold moisture content cloudy and clear humid & dry precipitation drizzles & downpours snowfall, snowpack, & snowmelt wind blizzards, tornadoes, & typhoons barometric pressure solar radiation

What is Climate Earth’s climate varies naturally over time and, to some extent, is always changing Climate change means altered patterns.

Global Climate Change IT IS NOT GCC describes trends in Earth’s climate, involving parameters such as temperature, precipitation, and storm frequency and intensity. IT IS NOT synonymous with the term Global Warming which refers to the gradual increase of the Earth’s temperature because of energy trapped by the Earth’s atmosphere. This is only one aspect of GCC The retention of the heat by the atmosphere is called the greenhouse effect.

Four Factors with Influence Sun Greenhouse Gasses Ocean Seasonal cycles Spin Tilt Orbit

Milankovitch Cycles Types of variation in Earth’s rotation and orbit that result in slight changes in the relative amount of solar radiation reaching Earth’s surface. Heat distribution patterns change Ice ages and other climate changes can be triggered

The Climate System Do humans have an affect on this?

Permanent gases Permanent gases in the atmosphere by percent are: Nitrogen 78.1% Oxygen 20.9% (Note that these two permanent gases together comprise 99% of the atmosphere) Other permanent gases: Argon 0.9% Neon 0.002% Helium % Krypton % Hydrogen %

Variable Gases in the Atmosphere Variable gases in the atmosphere and typical percentage values are: Water vapor 0 to 4% Carbon Dioxide 0.035% Methane % Ozone % CFC’s (not naturally occurring)

Earth’s Atmospheric Gases Nitrogen (N 2 ) Oxygen (O 2 ) Water (H 2 O) Carbon Dioxide (CO 2 ) Methane (CH 4 ) Non- Greenhouse Gases 99% Greenhouse Gases 1%

How Scientists Study Climate Change Evidence

How do we know? Ice Core DataTree Ring Data Coral Reef Biochemistry Sediment Core Data

How Do We Know? paleoclimate To have a baseline against which to measure changes happening to our climate today, scientists use paleoclimate evidence data from climate conditions in the geologic past. Proxy indicator – indirect evidence

Ice Core Data Examining trapped air bubbles in ice cores allows scientists to determine the atmospheric composition, greenhouse gas concentration, temperature trends, snowfall, and even frequency of forest fires and volcanic eruptions at the time these bubbles of gas were trapped.

Ice Core Data

Tree Ring Data By examining the width of each tree ring, scientists can determine the amount of precipitation available for plant growth deo/science_2/ /anci ent-tree-ring-data/

Bristlecone Pine (USA) – up to years old Tree Ring Data

Coral Reef Biochemistry Because living corals take in trace elements from ocean water as they grow, their growth bands give clues to ocean conditions at the time the bands were deposited in the coral skeleton. om/video/environment/habitats- environment/habitats-oceans- env/coral-reefs/

Sediment Core Data Sediments often preserve pollen grains from plants that grew in the past. Because climate influences the types of plants that grow in an area, knowing what plants were present cal tell us a great deal about the past climate at that place and time. ontexts/Dating-the-Past/Sci- Media/Video/Sediment-core-tour

Direct Measurements We know about the present changes from observations taken at the surface and in the atmosphere One of the questions often asked is if the warming isn’t an artifact of urban heat islands or changes in how measurements are done. Scientists have looked at this extensively. For example, when a NASA group removed all but 200 true rural sites, the warming pattern persisted. a U.S. National Climatic Data Center study found no statistically significant urban heat island effect in 289 U.S. stations. And finally, even though there are no cities in the oceans, warming has been measured over them too.

Climate Models Much like the models used to forecast weather, climate models simulate the climate system with a 3-dimensional grid that extends through the land, ocean, and atmosphere. The grid may have 10 to 60 different levels in the atmosphere and surface grid spacings of about 60 by 90 miles (100 by 150 km)—the size of Connecticut. The models perform trillions of calculations that describe changes in many climate factors in the grid.

Climate Models The models project possible climates based on scenarios that cover a range of assumptions about global population, greenhouse gas emissions, technologies, fuel sources, etc. The model results provide a range of possible impacts based on these assumptions.

Climate Models A common critique of climate predictions is, “If weather model forecasts aren’t reliable more than a week out, how can models predict climate decades in the future?” While weather and climate models are based on similar physics, they are not predicting the same thing. Weather forecasts look at the day-to-day changes on a local level, and subtle chaotic atmospheric variations make short-term weather forecasts difficult beyond 8-10 days. Aspen, CO Forecast: Partly cloudy today High : 28°F Low: 13°F Increasing clouds over night. Colder tomorrow.

Climate Models Climate predictions are focused on longer-term influences of the sun, oceans, land, and ice on the atmosphere. Instead of predicting a temperature at a particular place at a particular hour, climate modules project an average temperature over a year or longer in a large region or over the entire globe.

Climate Models Climate models are not only used to look at how climate might change, they’re also used to figure out WHY it’s changing. When models are run with only natural influences from the sun and volcanic eruptions, they say that during the latter half of the 20 th century, we would have expected little change from normal conditions (the blue line). Only the addition of human emissions (greenhouse gases, sulfates, and ozone) produce the model results in red that most closely reproduce the black line of actual observations.

Climate Models So, although they aren’t perfect, climate models can reproduce many of the larger features of climate change in Earth’s distant past, and they replicate the pattern of warming in the last 100+ years. This gives us confidence that they correctly identify that the warming is due to man’s activities, and that projections of future warming are realistic.

Earth’s Changing Climate Habitable Planet: nit/text.php?unit=12&secNum=1