It's Happening
Define a temperature anomaly.
The difference between the observed/recorded temperature and the expected or long term average temperature.
True or False: Solar radiation has increased in the past century or so, contributing to global warming.
False. Solar radiation has actually been decreasing, and variations in solar radiation are generally very minimal.
Is the methane/permafrost feedback positive or negative?
Bonus: Explain why it is positive or negative.
The methane/permafrost feedback is a positive feedback.
Warming will lead to the thawing of permafrost and exposure of organic matter to anaerobic conditions, leading to the formation of methane that will increase the greenhouse effect and lead to more warming.
List the 5 major components of the climate system.
The climate system includes the Biosphere, Hydrosphere, Atmosphere, Cryosphere, and Geosphere.
List the four primary controls on emissions.
Population, affluence, carbon intensity, energy intensity.
Bonus: describe each one and their recent trends.
What is the definition of climate? Weather?
Climate: Long term averages of weather for a given area, measured over the span of decades.
Weather: Current atmospheric conditions at a specific time/place.
What drives glacial/interglacial cycles?
Milankovitch cycles / changes in earth's orbit.
Bonus: What are each of the Milankovitch cycles, and how long is their combined/overall cycle?
How do greenhouse gases interact with visible light? Ultraviolet light? Infrared light?
Greenhouse gases transmit (are transparent to) ultraviolet and visible light, but absorb infrared light. They then re-emit this infrared radiation in all directions, reflecting some back to earth's surface.
How much has global average surface temperature increased compared to pre-industrial times? What is the concentration of carbon dioxide now and pre-industrialization?
Global average surface temperature has increased by 1.1 degrees Celsius since pre-industrial times. Before industrialization, carbon dioxide had a concentration of 280 ppm, which has risen to 425 ppm.
Differentiate between carbon dioxide emissions and carbon dioxide concentrations. What happens to concentrations when emissions reach net zero?
Carbon dioxide emissions are the amount of carbon dioxide entering the atmosphere per unit time (usually year). Concentrations are the actual amount of carbon dioxide in the atmosphere (usually in ppm). When emissions reach net zero, concentrations will stabilize/decrease slowly.
Describe the pace of warming over the past 150 years. (e.g. has it been consistent, accelerating, etc)
Global warming has exhibited two-step warming, with an initial warming phase followed by stable or slightly decreasing temperatures, then warming at an increased rate.
Bonus: what caused this two step warming / decades of stability/cooling?
Define and distinguish between detection and attribution. How are these ideas applied in climate science?
Detection is the process of identifying that conditions are changing/have changed, something is out of the ordinary. Attribution is identifying the cause of those changes. In climate science, detection refers to demonstrating that climate has changed, while attribution determines the most likely cause of that change (human activity).
What trend has been observed in lower stratospheric temperatures, and how does this relate to greenhouse gases?
The lower stratosphere has cooled, which indicates a buildup of greenhouse gases and a strengthened greenhouse effect, as less infrared radiation reaches the stratosphere to warm it (the energy is trapped closer to the earth's surface).
Describe the major sources of anthropogenic carbon dioxide emissions historically and in the present. Which countries are major emitters historically and in the present?
Historically, emissions came mostly from land use changes and coal, and the largest emitters were the U.S. and England. Presently, natural gas and oil are the largest source of emissions, and the U.S., China, and India are major sources of emissions.
Describe what an SSP is generally, and what the number after the dash means.
An SSP is a general "storyline" that describes what will happen on a global scale in the future with emissions and technology, like a significant shift towards sustainability, global competition, or a fossil fuel resurgence. The number indicates the radiative forcing, or difference between incoming and outgoing radiation, of that scenario in watts per meter squared.
List at least one non-temperature observation in 4 of the 5 spheres of the climate system (excluding geosphere) that indicate a changing climate.
Biosphere: organisms shifting to higher latitudes/elevation
Cryosphere: less sea ice
Hydrosphere: acidifying oceans
Atmosphere: changes in circulation
Describe the effect of volcanic eruptions on climate. What factors change how much volcanoes affect climate? What is the primary mechanism by which volcanoes influence climate?
Volcanoes generally cool the planet. Eruptions closer to the equator and that reach the stratosphere generally result in more cooling than polar or smaller eruptions, and more eruptions in a short time period can cause significant cooling, while less eruptions can lead to warming. They exert these effects by introducing aerosols into the atmosphere.
Which greenhouse gas is the major contributor to the natural greenhouse effect? Which is the major contributor to the anthropogenic greenhouse effect? Why do we care so much about this particular greenhouse gas?
Water vapor is the major contributor to the natural greenhouse effect, while carbon dioxide accounts for the anthropogenic greenhouse effect. Carbon dioxide has a long residence time and is the major greenhouse gas emitted by humans, and we have more control over it than water vapor.
Explain the two major ways in which aerosols affect climate.
Aerosols can cool the earth by directly absorbing and scattering incoming radiation in the atmosphere (the direct effect), and can act as cloud nucleation sites, creating more reflective and longer lasting clouds that can reduce incoming solar radiation.
How much warming is expected by the end of the century under the low, medium, and high emissions scenarios, and how is this warming distributed across the earth?
In the low emissions scenario, less than two degrees Celsius of warming is expected, while three degrees is expected in the medium scenario and four or more is expected in the high scenario. The Arctic will warm more than other areas, and land will generally warm more than the oceans.
Describe the Urban Heat Island effect, why it occurs, and how it is accounted for in measurements of global average surface temperature. Is it the cause of global warming?
It is caused by the high heat capacity of urban materials like concrete and asphalt, which can store more heat and release it overnight, as well as the concentration of human activities.
It is accounted for by using area weighted temperature calculations.
No, although it can play a part, it is not the sole cause of global warming.
Describe the benefits of studying the paleoclimate, and why it is important for understanding climate change today.
Studying the paleoclimate helps establish a baseline, reveal long term climate cycles, allows us to compare current warming to past warming, and lets us estimate how conditions might be in the future based on current and projected warming.
By how much does atmospheric carbon dioxide concentration change annually? How do concentrations change throughout the year, and why is this the case?
Atmospheric carbon dioxide concentrations increase by 2 ppm annually, with an increase of 7 ppm from the northern hemisphere late fall to early spring, and a decrease of 5 ppm from early spring to late fall. This seasonality exists because of photosynthesis by plants in the northern hemisphere, where there is significantly more land, which is increased during the northern hemisphere growing season and decreased during the cold months in the northern hemisphere.
Describe positive and negative feedback, and give at least one example of each that is related to climate. Explain how both types of feedback interact with initial warming or cooling.
Positive feedback increases the initial change, while negative feedback dampens or does the opposite of the initial change. One positive feedback in climate is the ice-albedo feedback, and a negative feedback is the rock weathering feedback.
In positive feedback, the initial response will be amplified, so warming will lead to more warming, while cooling will lead to more cooling. The opposite is true for negative feedbacks, which dampen the initial effect; initial warming will lead to cooling, and initial cooling will lead to warming.
Explain how climate models work to predict climatic conditions in the future. How do we test them, and can we trust them? What are they best and worst at simulating?
Climate models use mathematical equations that represent the physical laws of the climate system to take certain inputs (boundary conditions) like atmospheric conditions, solar radiation, etc. and calculate resulting conditions like temperature and precipitation. They are tested by having them simulate past climate change, and comparing their outputs to observed or inferred change. They are generally trustworthy, as their outputs agree with what we know or have observed about past climates. They are best at simulating temperature, and struggle to simulate all the effects of clouds.