Climate change impacts

Week 7 – August 3rd, 2020


Discussion #3 this week

Course Evaluations open Aug 5th!

Even though they are housed in Canvas, I have no access to them, so they are truly confidential.

Readings with Lecture

Audio interview of Ama Francis on climate-induced migration (2019) (https://www.yaleclimateconnections.org/2019/12/hurricane-maria-ravaged-her-island-nation-now-protect-climate-migrants/)

The Dakota Access Pipeline, Environmental Injustice, and US Settler Colonialism Kyle Powys Whyte (2017) – PDF on Canvas

Lecture Outline

We can expect climate change to result in the following (and many more…):

Human health impacts

Sea-level impacts (briefly)

Ecosystem impacts

Representative Concentration Pathways and projections into the future

And we’re off! Let’s start with humans because that’s what we often connect strongest with….

Human Health

Direct effects of climate change to human health:

Thermal stress, heat waves, floods, storm events

Any others you can think of?

Indirect effects:

Changes in range and seasonality of vector-borne diseases

Malaria, dengue-fever, salmonellosis, etc…

Water and air quality changes (often negative)

Food availability and shortages

Human Health, A Story…

Have you ever lived in an area that had water shut-off periods?

While conducting fieldwork in New Mexico in July 2015, the region we were in was placed under a fire and water ban. Absolutely no fires allowed *for any reason* AND from 12-4pm during the summer, all water to the town was shut off.

The fire ban is obvious, but why the water ban? Why shut off water to a town in NM in summer!? That seems horrifying, no?

Because if water is drawn to the surface, or already on the surface, during peak temperatures of the day, there is vastly increased rates of evapotranspiration (water loss from soil to air).

Thus, turning on your taps, watering lawns, flushing toilets, could not happen during peak evaporation periods.

Oh, and I forgot to mention….this town was in the middle of nowhere (i.e. closest store like a Walmart was about 50 miles away). If you needed water from 12-4pm and you didn’t have your own jugs stored….well….you better hope you had a nice neighbor…

Water security issues already exist in this country, we just often have the infrastructure and civilization set up to provide places to buy water whenever we need it. Thus the risk appears muted because of the security net, but what happens when the net fails, or you live in an area with no net at all?

Human Health

Here’s a graph from a study done in New Zealand that found the relationship between salmonella outbreaks and temperature

Notice that with increased temps, you get an increase in number of Salmonella cases.

These kinds of disease-temp relationships exist everywhere, and often are expedited in areas of flooding.

Human Health

“Developing countries are poorly equipped to deal with weather extremes…” (here’s a snippet from the IPCC AR3, similar results were found in AR4 and AR5…)

Human Health

Again, we see the connections between people and water. In this case, the presence (or absence) of water leads to stressors down the line. Add in more and more people into the 21st century and you have a water security problem…

From the IPCC AR(4)—

“the number of people living in ‘severely stressed’ river basins will increase drastically, namely by one to two billion by 2050s.”

Sea-Level Rise

Loss of coastlines (this is a biggie)

Did you know the coast of Louisiana on US maps is actually fake? The coastline of LA no longer looks like the bottom of a ”boot,” but rather a shredded shoe as more and more islands and channels are formed with sea level rise and coastal erosion!

Political ramifications (the biggest biggie) – what happens to island nations when there literally is no land left to build, no higher ground to find? Climate refugees are the result

I *highly* recommend reading the book Storming the Wall by Todd Miller – it’s a fantastic expose into the future of borderlands in a world of ever-changing climates.

More frequent and pervasive saltwater incursions into freshwater aquifers and leads to delta habitat loss

…this list is almost endless and we find new problems with sea level rise all the time…

Interested in learning more?!

I could spend an entire class on sea level rise and the Earth’s oceans, but like the details on climate modelling, we just don’t have the time in our term to dig much deeper.

Dr. Stephen Tsikalas teaches a class called Intro to Oceanography (GEOG 305)

I highly recommend taking it if you want to learn more on this topic! His email is: [email protected] if you’d like to reach out to him.

So we know what to expect from sea level rise and thermal expansion.

And from our experiences living on this planet for the past decade(s) or so, we know that climate change can impact our own health.

But how are things like forests and deserts and all the rest expected to change? Or how have they already started transitioning?

Ecosystem Changes

According to the IPCC AR(4) –

“During the course of this century the resilience of many ecosystems (their ability to adapt naturally) is likely to be exceeded by an unprecedented combination of change in climate, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification), and other global change drivers (e.g., land-use change, pollution, over-exploitation of resources.”

Ecosystem Changes


Vegetation is well-adapted, but only to a point

We will see increases in dune migration

Succulent Karoo of South Africa

2,800 endemic species

These species are found nowhere else on Earth!

2 deg C would cause a loss of 80% of habitat!!!

Ecosystem Changes

Grasslands and Savannas

Closely tied to precipitation regime shifts

Too much rain = forest, too little rain = desertification

Drought and fires will impact these ecosystems the most

Ecosystem Changes


Usually the drier/warmer coastal areas like California, Australia, and the Mediterranean

Habitat loss due to sea level rise

Fire frequency increases

Ecosystem Change


A Case Study on fire in the Hollywood hills!

Fire suppression, climate change, and natural plant ecology

Ecosystem Changes

Forests and Woodlands

Require certain temperature and precipitation regime stabilities

Too cold you get a conifer forest, not enough water you get a grassland, etc…

Drought, fire, and insect outbreak vulnerabilities will increase (or already have)

Deforestation is also releasing massive amounts of CO2 back to the atmosphere

Ecosystem Changes

Forests and Woodlands

Forest productivity due to CO2 fertilization

Tree-line increases

Ecosystem Changes

Forests and Woodlands

Range expansions in some areas at first

increased warming will offset northern expansion with tropical area loss

Rate of adaptation is outpaced by rate of climate change

Some climate models show complete Amazonian rainforest collapse…

Ecosystem Changes

Tundra and Arctic/Antarctic

Extreme levels of habitat loss

Food web collapse in high latitudes

Polar bears may only be found in zoos in the future

charismatic megafauna

Interested in learning more?

I teach two upper level courses on biogeography, ecosystems, and disturbances like wildfires.

GEOG 306 – Natural Vegetative Ecology

GEOG 421 – Dendrochronology

Both classes are 5 credit lab courses with field components. We explore topics of paleoenvironments, climate change, and wildfires.

Email me if you have questions or would like to see a syllabus! 

Ecosystem Changes

Freshwater Ecosystems

Stratification phenomenon in layers of non-flowing water

Decrease in oxygen availability

No lake turnovers

Loss of lakes in arctic and tropical regions

Ecosystem Changes

Oceans and Coastal Seas

Warming water, reduced nutrient contents, sea level rise, loss of ice cover, increased disease risk, acidification, etc.

Arctic Ocean productivity depends on sea ice cover

Food web collapse through trophic cascades

No more Deadliest Catch!

Ecosystem Changes

Oceans and Coastal Seas

Poleward shifts in marine fauna ranges

Warmer water can be found farther north

North Atlantic plankton now found 1,000 km farther north than 40 years ago

Coral Reef Bleaching

Balances in symbiotic relationships

1998 saw a loss of 16% of worlds coral

Ecosystem Changes

Great Barrier Reef and loss of Ecotourism

Ok, but how do we know just how bad it’s going to get? Is there a way we can look at a spread of possibilities? Can we look at future projections of change based on different levels of fossil fuel emissions?

Yes you can! They’re called Representative Concentration Pathways, and we have created four of them, each representing different futures under different carbon in the atmosphere….

Let’s check them out now!

Representative Concentration Pathways

RCPs are different pathways Earth’s system can take under different concentrations of carbon.

According to NOAA: “Representative Concentration Pathways (RCPs) are not new, fully integrated scenarios (i.e., they are not a complete package of socioeconomic, emissions and climate projections). They are consistent sets of projections of only the components of radiative forcing that are meant to serve as input for climate modeling, pattern scaling and atmospheric chemistry modeling”

The four different pathways are:

RCP 2.6

RCP 4.5

RCP 6.0

RCP 8.5

The numbers reflect W/m2 (watts per meter sq) and indicate radiative forcing units at Earth’s surface. You do not need to know anything beyond that for this class.

Anthropogenic Radiative Forcing

Measure of how much positive (notice y axis) impact each RCP has on atm radiative change

Positive forcing = increase in radiation of heat within atmosphere

This positive forcing leads to positive increases in atmospheric temperatures

Ignore the SRES models, we don’t cover them in this class…

RCPs and atm [CO2]

The most conservative scenario is the RCP 2.6 = strong reductions post 2020

Well…we’re here in 2020, how do you think we’re doing on this scenario???

The worst case scenario is the RCP8.5 = Business as Usual (BAU) until 2100

We’ve done nothing but pursue this pathway for the past 4 years.

Check out on the graph what each potential RCP means for fossil fuel emissions and atmospheric carbon

Atm [CO2] and Global Temp Response

Carbon emission scenarios used in GCMs to project future global temp responses


Variability to Warming

In the Business As Usual (BAU) scenario (the RCP8.5)

More warming over land than water

More warming in Arctic than elsewhere – but equatorial mid/upper troposphere will experience increased temp change too

This does NOT mean the Arctic is warmer than the tropics, it means there has been more change in temp in the Arctic than in the tropics!

Arctic Sea Ice Extent via RCPs

And look what each RCP means for the ice!!

RCP2.6 shows substantial ice over

RCP8.5 shows almost ice-free Arctic

There are times in the year now when areas of the Arctic are already completely ice free…

Global Sea Level Rise Projections

Based on whatever RCP ends up happening, we can also see changes to sea level rise…

Spread in scenario projects exist due to uncertainties in GCMs related to future projects of temperature

This does NOT mean models are wrong, it’s simply caution used in science!

Ok that’s all for this week! Don’t forget to do the two extra readings and watch the documentaries for discussion this week!

Links to Check Out!

Climate Models and RCPs via NOAA


This is the RCP2.6, but you’ll notice if you scroll down you can see pages for each of the other three.

RCP database (continually updated)


Looking Ahead

Last week of term!

Discussion #4 is the same as the setup for #2, where you write and answer essay questions for your peers.

Exam #2 will be due Friday, Aug 14th and will be the same format as Exam #1

Don’t hesitate to reach out with questions or concerns!