Week 8
diagram of Possible temperatures by 2100 with various carbon emission scenarios (wedge diagram)
shows the actual temp change and then projects into the future under 4 different scenarios called RCPs. projects expected temps depending on if we cut/increase etc co2 emissions
1. CO2 sticks around!
CO2 remains in the atmosphere longer than the other major heat-trapping gases emitted as a result of human activities. It takes about a decade for methane (CH4) emissions to leave the atmosphere (it converts into CO2). It takes about a century for nitrous oxide (N2O) emissions to leave the atmosphere. It takes about a century for most CO2 emissions to leave the atmosphere, but about 20 percent will still exist in the atmosphere approximately 800 years from now.
How do we measure CO2 in the atmosphere? (to show that it is increasing)
Carbon dioxide in the atmosphere is measured at Mauna Loa Observatory, Hawaii. The Observatory is near the summit of Mauna Loa, at an altitude of 3400 m, and is well situated to measure air masses that are representative of very large areas.
What is the cause of current climate change?
Anthropogenic (human caused) emissions of greenhouse gases (GHGs): carbon dioxide (CO2) methane (CH4) nitrous oxide (N2O) These three GHGs have increased in the atmosphere since pre-industrial times (1750).
Birds + trophic mismatch example +climate change
Migratory species such as birds depend on that annual flush of food for their breeding success. If they arrive and the insects they expected are not hatched yet then there is a tropic mismatch. Birds are adapted to a set of conditions in a habitat as defined by temperature, moisture and the interspecific interactions that occur there Climate change causes these conditions to change and so birds, if they have the option, will move.............to smaller spaces with limited or different resources and increased competition and possibly new predators
Is stopping fossil fuel emissions enough to cool the planet? If not, what has to be done in addition to stopping fossil fuel emissions?
No. To cool the planet in this century, humans must either remove carbon from the air or use solar geoengineering, a temporary measure that may reduce peak temperatures, extreme storms and other climatic changes. Humans might make the planet Earth more reflective by adding tiny sulfuric acid droplets to the stratosphere from aircraft, whitening low-level clouds over the ocean by spraying sea salt into the air, or other methods.
effects graph
graph showing increased temps, higher sea levels, and melting snow cover
The "hockey stick" graph:
shows baseline at zero, and then all the departures. shows that after industrial revolution temps are above baseline average temperatures in the northern hemisphere hold roughly steady for 900 years or so, until the 20th century, when they rise sharply. Basic premise = the planet's recent warming is unprecedented over at least the last millennium.
penology graph
shows that invertebrates are doing their activities earlier, amphibians are too, everything, trees not much earlier though, the rest are way earlier so now theres mismatch
climate surface warming and cooling influence by human-induced climate drivers
zero line is where it doesnt impact the climate. above is something that warms the surface of the earth, below is something that cools warmers: carbon dioxide, methane, nitrous oxide, halocarbons, tropospheric ozone coolers: aerosols, albedo,
The keeling curve
zig zags show seasons when forests are dormant and awake and co2 fluctuates. the curve shows the seasonal average of atmospheric co2 increasing
Carbon dioxide (CO2), more than any other GHG, has contributed the most to climate change between 1750 and 2005. Why?
1. CO2 sticks around! 2. CO2 has the highest positive radiative forcing (RF) of all the human-influenced climate drivers. (RF is the measurement of surface warming ability)
What is a carbon footprint?
A carbon footprint is the total amount of greenhouse gas emissions that come from the production, use and end-of-life of a product or service. It includes carbon dioxide — the gas most commonly emitted by humans — and others, including methane, nitrous oxide, and fluorinated gases, which trap heat in the atmosphere, causing global warming. Usually, the bulk of an individual's carbon footprint will come from transportation, housing and food.
why we need climate models
Computer models, while imperfect, may be the best shot we have for learning what climate change will bring. We all know the world is a complex place. The best way to understand some of that complexity is to break it down into smaller components. Once these smaller parts are understood, we can combine them in ways that help us understand how they work together—similar to how fitting puzzle pieces together enables us to see the bigger picture. Scientists use computer models, made up of many "smaller parts," to help us understand such complexities as hurricane paths, fish populations, and the climate system. When models do a good job replicating past and current events, we assume they are able to forecast, with reasonable certainty, what might happen in the future.....................
Future warming:
Computer simulations of temperature change in response to greenhouse gas concentrations are the best predictive tool of future climate change.
What can you do to reduce your carbon footprint?
Drive less, fly less, carpool, use cruise control, go easy on gas and breaks, get car serviced regularly, cut down on AC and intensive city driving. Eat less meat, waste less, use real dishes instead of disposable ones, turn off lights when not being used, don't set fridge temps too low, recycle, dress and shop sustainably (bring own bag, only buy things that'll last, thrift).
How do we know what will happen in the future?
Global Climate Models (GCMs)
Observed changes
Increase in Earth's average temperature Changes in the patterns and amounts of precipitation Reduced ice and snow cover, as well as permafrost (bc melting) Raised sea level (bc melting of ice and snow) Increased acidity of the oceans Increased frequency, intensity, and/or duration of extreme events Shifted ecosystem characteristics Increased threats to human health These changes impact our food supply, water resources, infrastructure, ecosystems, and even our own health.
What is different about the current temperature change compared to past climate change?
Magnitude and rate Higher concentrations now of atmospheric CO2, CH4 and N2O than any level recorded in the 800,000 year ice core record. The higher average rate of increase of these three gases observed over the past century exceeds any observed rate of change over the previous 20,000 years.
2. CO2 has the highest positive radiative forcing (RF) of all the human-influenced climate drivers. (RF is the measurement of surface warming ability)
Other gases have more potent heat-trapping ability molecule per molecule than CO2 (e.g. methane), but are simply far less abundant in the atmosphere and are being added more slowly.
IPCC report Look at Fig 1 panels a and b on page 7 and write a few sentences on what they are showing.
The two panels show together that human influence has warmed the climate at a rate that is unprecedented in at least the last 2000 years. They do this by showing the changes in global surface temperatures over the past 2000 years relative to 1850-1900. The first panel shows changes in global surface temperatures reconstructed from paleoclimate archives and from direct observations, both relative to 1850-1900 and decadally averaged over the last 2000 years. The second panel shows the changes in global surface temperatures (annual average) as observed and simulated using human & natural and only natural factors over the past 170 years (1850-2020).
Look at Fig 2 panels a and b and c on page 8 and write a few sentences on what they are showing.
The panels show together that observed warming is driven by emissions from human activities, with greenhouse gas warming partly masked by aerosol cooling. Panel 1 shows the observed global warming 2010-2019 relative to 1850-1900. The second panel shows the aggregated contributions to 2010-2019 warming relative to 1850-1900. It shows how the temperature change is attributed to total human influence, changes in well-mixed greenhouse gas concentrations, other human drivers due to aerosols, ozone and land-use change (land-use reflectance), solar and volcanic drivers, and internal climate variability. The third panel shows the contributions to 2010-2019 warming relative to 1850-1900, assessed from radiative forcing studies, showing evidence of temperature changes from individual components of human influence, including emissions of greenhouse gases, aerosols and their precursors; land-use changes (land-use reflectance and irrigation); and aviation contrails.
Have these high concentrations of CO2 and these high temperatures been seen before?
We can look back at past CO2 concentrations and temperatures (before humans started direct measurements). An 800,000 year record comes from Dome C in Antarctica.
Is the earth warming? IPCC evidence
Yes. (What is IPCC? The UN Intergovernmental Panel on Climate Change is an international group of scientists that assesses research on climate change and summarizes it into 'assessment' reports.) Global Average Temperature projections from 1990 (0.15 C to 0.3 C increase per decade for 1990 to 2005) can now be compared with the actual observed values of about 0.2 C per decade! (aka they were right) This strengthens our confidence in projections. 2020: 2020 was effectively tied with 2016 for the hottest year on record The last decade was the warmest on record Small changes in the average temperature of the planet can translate to large and potentially dangerous shifts in climate and weather largely because of increased evaporation of water that then becomes available for storms For reference, climate models indicate that the Last Glacial Maximum was 3 C to 5 C cooler than the present; most recent data: Global cooling during LGM is 6 C. https://www.nature.com/articles/s41586-021-03467-6.pdf?origin=ppub The new estimates suggest greater sensitivity of the climate to atmospheric carbon dioxide than prior studies do: temperatures actually go up 3.4 degrees C (6.1 F) per doubling of CO2
Trophic mismatch
availability of food shifts in response to warming temperatures (ex migratory bird depending on food for breeding process but the things they eat aren't ready yet or east the point)
Where do these greenhouse gasses come from?
carbon dioxide CO2 from fossil fuel burning, agriculture (*deforestation, tilling soils, burning) methane CH4 from cattle, etc. nitrous oxide N2O from fertilizer pollution
What could you personally do to reduce CO2 emissions?
conserve light and heat (turn off lights and lower the heat) ride a bike, walk, or take public transportation if you buy a car, choose one with high fuel efficiency invest and shop wisely
What can be done?
shift to renewable energy sources increase energy efficiency start putting some of the CO2 away before it reaches the atmosphere (Carbon Capture and Sequestration CCS)
Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases.
snow, ice and frozen ground (including permafrost) melting warming of lakes and rivers Land biology: earlier timing of spring events, such as leaf-unfolding, bird migration and egg- laying = phenological changes poleward and upward shifts in ranges in plant and animal species, longer thermal growing seasons marine and freshwater biological systems (rising water temperatures, changes in ice cover, salinity, oxygen levels and circulation) shifts in ranges and changes in algal, plankton and fish abundance in high-latitude oceans; increases in algal and zooplankton abundance in high-latitude and high-altitude lakes; • range changes and earlier migrations of fish in rivers • ocean becoming more acidic: when CO2 dissolves in seawater most is used for PS and some reacts with H20 to form carbonic acid (H2CO3)
graph global temp anomalies NOA, NASA/GISS, and CRU
they reconstructed temps from 1800s to 2000 global surface air temperature trends shows same pattern that temps are above baseline after industrial reolution
What do the ice cores tell us?
they trap bubbles that have atmpspheric samples in them that lets us look at past atmospheric conditions 800,000 years of cyclical patterns: ice age/interglacial cycles Changes in carbon dioxide concentrations (in purple) track closely with changes in temperature (in blue) No past CO2 conc or Temp as high as today in the last 800,000 years. (Because it takes a while for snow to compress into ice, ice core data are not yet available much beyond the 18th century at most locations.)
ice age cycle graph
this is all from before the indusstrial revolution, the takeaway is that the temps and co2 concentrations are much higher now, co2 was 280 at highest, now 419 ppm
Phenology
timing of natural events (egg laying, flowering time, leaf fall)
