This question appears on AP Environmental Science exams and practice materials, where “Scenario 1” typically describes rising global temperatures driven by increasing greenhouse gas concentrations. The possible effects of climate change illustrated in such a scenario include sea level rise from thermal expansion, shifts in species ranges, more frequent extreme weather events, ocean acidification, glacier loss, and declining crop yields. Any of these can be the correct answer depending on the specific version of the question, so understanding how each one connects to rising temperatures is the key to getting it right.
Sea Level Rise From Thermal Expansion
When a scenario shows ocean temperatures climbing alongside atmospheric CO₂, the most direct physical consequence is thermal expansion. More than 90 percent of the extra heat trapped by greenhouse gases is absorbed by the oceans. As seawater warms, it physically expands in volume, pushing sea levels higher without any ice needing to melt at all. NASA measurements from satellite altimeters and a global network of ocean sensors called Argo floats show that thermal expansion has accounted for roughly one-third of observed sea level rise since 2004.
This matters because many exam scenarios pair a temperature graph with a sea level graph and ask you to identify the connection. Thermal expansion is the mechanism that links those two curves directly.
Species Range Shifts
A warming climate pushes species toward cooler areas, generally higher in elevation or closer to the poles. In tropical mountains, this effect is especially severe. Research on amphibians in Colombia’s Sierra Nevada de Santa Marta found that more than 30 percent of the range of 21 out of 46 species is likely to become thermally isolated as temperatures rise, meaning populations get stranded in shrinking cool zones with no viable path to cooler habitat. For seven species, over 70 percent of their current range would either become isolated or shift into areas that can’t support survival and reproduction.
If your scenario shows temperature bands moving upslope or poleward, the illustrated effect is a change in species distribution. Organisms that can’t move fast enough, or that hit barriers like deforested land or mountain peaks, face population collapse or extinction.
More Intense Extreme Weather
The frequency and intensity of heat extremes, including heatwaves, have increased globally since 1950. That trend holds across more than 80 percent of world regions assessed by the IPCC. At the same time, cold extremes have become less frequent. Evidence has also strengthened for links between human emissions and changes in extreme precipitation, droughts, tropical cyclones, and compound events like simultaneous heat and drought that fuel wildfires.
A warmer atmosphere holds more moisture, roughly 7 percent more per degree Celsius of warming. That extra moisture fuels heavier downpours even as shifting circulation patterns make some regions drier. When a scenario describes increasing global temperature and asks about weather patterns, the correct effect is typically an increase in the frequency or severity of extreme weather events.
Ocean Acidification
Rising CO₂ doesn’t just warm the planet. The ocean absorbs a large share of atmospheric carbon dioxide, and when CO₂ dissolves in seawater it forms carbonic acid, lowering the pH. Mean surface ocean pH is projected to drop between 0.15 and 0.5 units by 2100, depending on the emissions pathway. That range sounds small, but pH is a logarithmic scale, so even a 0.15 drop represents a meaningful increase in acidity.
Lower pH reduces the availability of calcium carbonate, the mineral that corals, mollusks, and certain plankton use to build shells and skeletons. Cold-water corals in the North Atlantic are expected to face particularly severe damage. If your scenario specifically mentions CO₂ concentration rising alongside ocean chemistry changes, acidification is the effect being illustrated.
Glacier Mass Loss
Mountain glaciers supply freshwater to nearly two billion people worldwide. Even under a best-case warming of 1.5°C, glaciers are projected to lose 26 percent of their mass by 2100 relative to 2015, with 49 percent of individual glaciers disappearing entirely. Under 4°C of warming, those numbers jump to 41 percent mass loss and 83 percent of glaciers gone. That lost ice translates to 90 to 154 millimeters of additional sea level rise on top of thermal expansion.
Glacier retreat also disrupts seasonal water supplies. Communities that depend on glacial meltwater during dry months lose that reliable source as glaciers shrink, creating water shortages even in regions that receive adequate annual rainfall.
Declining Crop Yields
Higher temperatures, shifting rainfall, and more frequent droughts reduce the productivity of staple crops. Modeling from Stanford researchers estimates that global calorie yields from staple crops would fall 11 percent by 2100 under rapid emissions cuts and 24 percent if emissions continue rising unchecked. Maize, wheat, and soybeans each face a 70 to 90 percent probability of yield declines by century’s end. Rice is the one partial exception, with roughly a 50 percent chance that yields could actually increase on a warmer planet, likely because rice thrives in warm, wet conditions that some regions will experience more of.
These yield declines persist even when the models account for farmers adapting by changing planting dates, switching crop varieties, or expanding irrigation. The adaptation helps, but it doesn’t fully offset the losses.
How to Identify the Correct Answer
The key is matching the data shown in Scenario 1 to the specific effect described in each answer choice. If the scenario shows rising ocean temperatures paired with coastline changes, the answer involves sea level rise. If it shows CO₂ levels alongside pH data, the answer is ocean acidification. If it shows temperature increases alongside biodiversity data, the answer relates to species range shifts or habitat loss.
Most versions of this question test whether you can trace a causal chain: greenhouse gas emissions lead to warming, warming leads to a physical or biological change, and that change produces a measurable consequence. The “possible effect” language in the question means the answer doesn’t have to be guaranteed, just plausible and supported by the scenario’s data. Look for the answer choice that follows logically from whatever variables Scenario 1 presents, and avoid choices that introduce factors not shown in the scenario.