Intergovernmental Panel on Climate Change (IPCC) I: Current Climate-Driven Impacts

Andy here –

Teaching about climate change this year took a toll on me. I’m normally a resilient and fairly hopeful person, but diving into the current and future impacts of climate change commonly leaves a person shell-shocked. How do climate scientists cope with existential dread?

Scientists are people too. Some of us are young, many of us have kids. It is difficult to stare this problem in the face day in and day out, without feeling like you are watching a slow motion train wreck, with your elected officials stepping on the gas rather than using the brakes. I’ve decided that I’m going to share those feelings with other people. We’re starting with the current impacts. A second post will follow with the basics of climate modeling, and finishing with what we think will happen next.

What follows here is a small, incomplete collection of current climate-driven impacts and assorted links to other information. I’ve tried to keep it to just impacts that are established in the Intergovernmental Panel on Climate Change (IPCC). These are things that science can firmly establish as happening right now due to climate change.

Hydrological (Water) Cycle

Data showing percent of days per year with much below normal rainfall amounts (brown bars) and much above normal rainfall (green bars) within the continuous U.S. Notice that as you move from 1910 to 2010, the length of the brown bars decreases, while the length of the green bars increases. This indicates that there has been increasingly more days with rainfall. Data from NOAA U.S. Climate Extremes Index (CIE).

We can currently say there are substantial changes to where and how rain and snow fall because of climate change. These changes have altered our ability to use water, both in quantity and quality. If we look at Michigan as an example, it has an increase in yearly precipitation of 2/3 of an inch per decade since 1960. Massachusetts has seen >1 inch per decade (data here). Other states are not as lucky, and are currently seeing a decrease (e.g., California). Our freshwater is increasingly contaminated due to both low (drought) and high (flood) conditions in many locations in the US. 10% of counties are currently under high or extreme risk of a water shortage.

We, as humans, are at the start of these changes as well.

If you’re curious what the US government has to say about water use changes, click here for the National Climate Assessment Water Use (from 2014) page. It also has very scary maps!

IPCC: In many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in terms of quantity and quality (medium confidence).

Click here to explore the National Climate Assessment site’s findings from 2014 on water supplies.


We can also say that animals, plants, and other organisms have had responses to climate change. Coral reefs are the easy and moderately better-known connection, what with nearly 50% of the Great Barrier Reef corals dead in the northern section. Polar bears are similarly simple. With the arctic warming faster than the globe, 3/19 tracked polar bear populations are shrinking, while we don’t have enough data to say anything about the other 9/19. At least one of the ‘stable’ populations has shrunk since 25 years ago (stability is a ~12 year average). More warm winters mean more ticks in moose territory. A warmer West coast means stressed salmon. And so on.

While a projection (estimation based on current data), which I’m trying to save until later, click here for a map visualizing how species will need to move to maintain their proper habitat in a climate-shifting world.

IPCC: Many terrestrial, freshwater, and marine species have shifted their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions in response to ongoing climate change (high confidence).


Climate change also has a negative effect on crop growth. Unlike what Lamar Smith has written (R-TX, head of the House Committee on Science, Space, and Technology), we do not expect there to be a benefit of increased CO2 in plant growth. Temperature effects far outweigh the small growth boost of higher CO2, and will lead to decreased seed yields. Climate change will shift where things grow; in some areas of India that used to get more snow there are new potato crops growing now with the milder winters. That’s good, but it’s quite the outlier. Wheat, rice, maize, soybean, barley and sorghum all respond negatively in rising temperature. Wheat production has already dropped 5.5%, and Maize by 3.8%. That is with our limited (in the face of what is projected) temperature changes so far.

Click here for an article by Scott Johnson that goes into more detail.

IPCC: Based on many studies covering a wide range of regions and crops, negative impacts of climate change on crop yields have been more common than positive impacts (high confidence).

Graph of projected increases (cool colors) and decreases (warm colors) of crop yields in the coming decades under increased warming. Notice how decreasing crop yields are more prevalent from 2010-2029 to 2090-2109. Image from IPCC (2014).

Extreme Weather Events

A) Percent of summer days when maximum temperatures exceeded long-term daily 95th percentile (the hottest recorded temperatures) from 1880 to 2005 over Western Europe. B) Heat wave intensity (number of days heat waves lasted) in Western Europe. Data from the Norwegian Meteorological Institute, 2013.

Climate change also increases the chances of having extreme weather events. Importantly, we can’t say that an individual hurricane is directly a result of climate change. We can say, however, that they are more likely. We can say that they’re made stronger, when they do happen. Harvey and others aren’t because of climate change but they’re more likely to happen and be worse because of it. Storms like Harvey, or Maria, or Irma, or Ophelia (which even hit the UK!) are more likely, and therefore more frequent, because of our warmer world.

Wildfires (click here for more details) are also made more common, due to drier conditions in some areas. So are floods, where there’s an increase in precipitation. And heatwaves. And on, and on.

This will obviously stress our systems to care for those affected. Given this summer and fall, I shouldn’t really need to back up that claim with supporting data.

IPCC: Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability (very high confidence).

Economic Impacts

Climate change has cost us money, and it will likely continue to cost us. We can say this with a high degree of certainty. Wildfires, floods, storms, droughts, earthquakes, tsunamis, all have a monetary cost. The insurance industry is well aware of the increasing trend in the costs, and so keeps track. We can divide the cost of these natural disasters into things that will be altered by climate change (wildfires, floods, storms, droughts, so on) and those not affected by climate change (earthquakes, tsunamis, etc.). This acts as a nice check against our buildings being more expensive, disaster relief being more expensive, or something like that. When we do this, all of the climate-related costs are increasing dramatically (click here for more details), while those not affected by climate change are only increasingly slightly. The number of climate-related (or extreme-weather) disasters is increasing, while the number of earthquakes is flat.

IPCC: Direct and insured losses from weather-related disasters have increased substantially in recent decades, both globally and regionally.

Ocean Temperature Changes

Top: Observed global annual averaged land and ocean surface temperature anomalies. Bottom: Same data as above, but decadal averages. Grey boxes represent uncertainty. Image from IPCC (2014).

Many of the ocean acidification impacts are similar or work alongside the impacts of increases in ocean temperature (click here for more details). Two examples: Corals bleach primarily due to temperature and their ‘skeletons’ fall apart in response to the pH. Similarly, when temperature rises, krill reproduce in smaller numbers. Krill are a key part of the food chain for things that people find cute, like penguins, seals, and many whales. Together, if those larger animals are stressed or starve, their predators die too.

Warmer water also expands, so a warmer ocean means that sea-level rise occurs more as well. This can magnify the storm surges, amplifies the effect of the melting glacial waters, and is generally a very bad thing.

Oh yeah, and the rate that the ocean is warming is accelerating.

Ocean Acidification

Many things have changed in the oceans due to the increase in carbon dioxide in the atmosphere. The first is that the ocean has absorbed quite a bit of that carbon dioxide. The pH has changed by 0.1 units since the industrial revolution. pH scales are not linear, so this actually is a 30% increase in acidity.

Marine life obviously feels this massive change. Because they are smaller and more fragile, larval stages of various organisms or plankton feel the effects first. While there are other things at issue (though research is working on detangling the others: water quality issues, low oxygen, or changes in diseases, etc.), the current rash of losses in the oyster industry are at least partially due to changes in acidity. The oyster industry is a $100-million-a-year industry. Click here for more details.

Corals, too, are stressed. Coral bleaching is due to temperature, but the material that corals make their skeletons out of is susceptible to acidification. It makes it harder for them to reproduce, grow, and live. They also dissolve and erode faster under higher amounts of acid.

There are currently more than a million other species living in coral reefs, making reefs some of the greatest spots of diversity on Earth.

Sea Level Rise

Top: Average sea ice extent in millions of km squared for the Arctic and Antarctica from 1900 to 2010. The Arctic is melting at an alarming rate. Bottom: Global average sea level rise in meters from 1900 to 2010. Image from IPCC (2014).

Sea level has risen between 10-25 centimeters. Because much of the coast is really flat, that means much more area has been lost than it appears. We think that the loss to property values is between $3-5 billion a year. In structural loss, it is $500 million. We spend a lot of money to keep the coast where it is too; like the $14 billion Louisiana is expecting to put into coastal barriers along the Mississippi River delta. In other areas, the coast just erodes and land disappears into the ocean. Click here for more details.

Click here for a neat NOAA page that lets you see what happens as sea level rises.

We know sea level rise also has a cost on communities and lives. An entire community, Shishmaref in Alaska, has lost 2,500 to 3,000 feet of land in 35 years. Other communities, Kivalina, Newtok, Shaktoolik, and others (31 in total) need to be moved according to the Army Corps of Engineers. At least one community has voted to move to the mainland, but without funding to move, cannot.

Marginalized Communities

Climate change is a volume knob for social justice issues. That volume knob is sensitive.

Communities that are marginalized (have less political power, less money, etc.) are far more at risk in a changing world. If you have less power in society, odds are that a society under stress from climate change will be less likely to support you in the face of needs (even a lesser need) of a more powerful,other group.

This is referred to as ‘Climate Justice’. The People’s Climate March in Washington, D.C. (2017) was a wonderful example of how this has been embraced. From what I could tell, there were far more people there interested in social justice (indigenous communities, religious communities, etc.) than the scientists or folks who allied themselves with science at the march. It’s called the People’s Climate March for a reason. Click here for the NAACP’s page on Climate and Environmental Justice.

There is no clearer example than what happened and is currently happening in the US in 2017. Puerto Rico is not a state. Florida and Texas are. The US response to Puerto Rico which, again, is a part of the United States of America is the textbook example of this. Puerto Rico does not have representation in the federal government, so is ‘less important’ from a hardline (and inhumane) political point of view. The differing response from the federal government is a direct and obvious example of this IPCC finding.

Click here for more details on climate justice.

IPCC: Differences in vulnerability and exposure arise from non-climatic factors and from multidimensional inequalities often produced by uneven development processes (very high confidence). These differences shape differential risks from climate change.


Climate change is currently changing the water cycle, changing how water resources can be accessed. We’ve seen that animals and plants are already shifting their habitats due to climate change. A specific, but very human-centric part of that is how crops are and will respond. Harvests, in bulk, are down for many of our grains. Climate change has already cost us lots of money, and will continue to.

Lastly, but probably most importantly, climate change is currently felt by disadvantaged peoples disproportionately. The US response to Puerto Rico which is a part of the US is the textbook example of this. Puerto Rico does not have statehood, so is ‘less important’ from a hardline (and inhumane) political point of view.

We cannot, scientifically, say that Maria and Harvey and Irma and Ophelia are because of climate change. Attribution is difficult due to the statistics involved. We can however say that the scientific prediction for what happens in a warmer world is larger, more damaging and frequent storms. That is what we experienced in 2017.


IPCC, 2014. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II, and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Core Writing Team, R.K. Pachauri and L.A. Meyer, eds.). IPCC, Geneva, Switzerland, 151 pp.

‘Extreme Climate Events in Europe: preparing for climate change adaptation”, 2013. Norwegian Meteorlogical Institute, Oslow, Norway, 140 pp. 

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