Heatwaves, Climate Scenarios, and How We Talk About Them

In May, parts of the UK and France are experiencing a heatwave that feels like mid‑summer, even though it’s spring. A high‑pressure system—a heat dome—has driven temperatures up, mirroring similar events in India and Canada. Across the Atlantic, the United States has endured one of its worst spring droughts, only to be hit by sudden heavy rains that closed major highways in Atlanta. These events underscore that climate extremes are already a reality.

RCP8.5: The “Worst‑Case” Scenario

Scientists often use Representative Concentration Pathways (RCPs) to model future climate outcomes. RCP8.5, the most talked‑about scenario, was designed to illustrate an upper bound of possible emissions—burning all the world’s coal and ignoring clean energy. It is not a prediction that we will reach it, but an illustration of the maximum risk.

A recent UN report indicates RCP8.5 is unlikely because real‑world policies and cheaper clean energy are driving emissions down. While this may feel like a victory, it can also breed confusion: people might think the danger has vanished when many other serious outcomes remain.

The Misleading Simplicity of RCP8.5

Headlines and some scientists continue to reference RCP8.5 without context, leading the public to believe the climate crisis is over. In reality, we’re still on a trajectory that could add 2–3 °C of warming if emissions stay high. Researchers now favor more realistic ranges—RCP4.5 or RCP6—which still show significant impacts on weather, sea level, agriculture, and infrastructure.

A Helpful Analogy

One thinker likened the situation to a night out at a bar: sipping soda or a few beers is fine, but continuing to drink and then driving dramatically increases risk. RCP8.5 is like the hypothetical scenario of never drinking all the beer—a situation that doesn’t happen—yet other risky behaviors, such as burning fossil fuels, still exist. Removing the extreme scenario from discussion is good, but it doesn’t erase the many ways climate change can worsen.

The Bottom Line

We still need to cut emissions and maintain a full discussion of all possible outcomes—not just the most extreme. Understanding the entire range of scenarios helps policymakers, businesses, and citizens decide how to act before problems become unmanageable.