A Washington Post analysis of four global temperature data sets, spanning from the 1800s to the present, has found that dangerous hot spots are spreading around the planet — on land and in the oceans alike.

The analysis, using data from U.S. federal scientists as well as several academic groups, finds that over the past five years — the hottest on record — about 10 percent of the planet has exceeded warming of over 2 degrees Celsius, or 3.6 degrees Fahrenheit.

Scientists have identified this as a clear line that the planet as a whole must not cross. But in some locations, it has already happened.

Areas that have warmed by 1.5 degrees Celsius — another crucial marker — are about twice as common. And thus, in many of the scenarios that we considered, they already exceed 20 percent of the Earth’s area over in the last five years.

Here’s some more detail on what we found:

1. Pick your favored time periods — many regions have already crossed 2C. Defining how much warming has occurred requires choosing two separate time periods to compare. In our case, we considered two “preindustrial” periods — 1850 to 1899 and 1880 to 1899 — and two end periods, 2014 to 2018 and 2009 to 2018. Some choices clearly push more of the globe across 2C — especially selecting the very warm years between 2014 and 2018. But the lowest total we got for how much of the globe is above 2C was about 5 percent. That’s still an enormous area.

2. It’s not just about the Arctic anymore. We have known for a long time that the fastest-warming part of the world is the Arctic. Our analysis supports that and shows that huge swaths of the region are above 2C — if not above 3C. But we also find that much more than just the Arctic has crossed this threshold. Depending on the analysis used, we see 2C of warming in much of Europe, northern Asia, the Middle East, and in key ocean hot zones.

3. Changes in ocean currents are creating dramatic hot zones. Huge ocean currents, which transport heat, salt, and nutrients around the globe, are on the move, driven by changes in winds and atmospheric circulation. And because these ocean currents are warm, when they reach new areas those areas heat up fast. This is a particular problem in the Southern Hemisphere where changes have occurred in every major ocean basin, leaving distinct hotspots in the regions of the Brazil Current (South Atlantic), the Agulhas Current (South Indian), and the East Australian Current (South Pacific).

Our story focuses on the Brazil Current, which shows a particularly rapid warming. But it’s not alone. The Agulhas Current, which travels southward along the coast of southeast Africa before swinging east towards Australia, shows a warming of well above 1.5C in many regions -- and occasionally even above 2C in some datasets and scenarios. Scientists have caught on to this change, and it is a big deal. The Agulhas is now spinning off more rings of warm water that swirl into the South Atlantic ocean, transporting heat and salt from the Indian Ocean and potentially impacting a global circulation of currents.

4. These high levels of warming present major risks. Our story focuses on Uruguay, where a fast-warming ocean hot spot, linked with the Brazil Current, has been linked to major disruption of marine ecosystems. Clams are dying along beaches, ocean heat waves are killing fish, algal blooms are worsening, and more. The entire fish catch for the country is now hauling up more tropical, warm-water-loving species, which is just what you would expect when dramatic ocean heating occurs in a region.

5. Fish can swim elsewhere. That’s not so easy for clams or corals … or people. When fast ocean warming occurs, some species may easily adjust — for instance, many fish swim toward the poles and cooler waters. But others don’t have such an easy time. Clams, for instance, are more or less stuck in place. So are corals. Moreover, many communities along coastlines are dependent on specific fisheries — meaning that for people, too, it can be very difficult to move or adjust. It is in these communities that many of the most dramatic consequences of climate change will be felt.

6. More of the globe will be at 2C — very soon. The Post’s method considers five- and 10-year averages to identify which regions have already eclipsed 2C. The past five years have been especially hot, so naturally, they show more of these hot spots.

But over the long term, both averages are marching steadily upward. It just takes a little while for the 10-year average to catch up.

Many factors influence the Earth’s climate, and not every year is automatically hotter than the next. But an upward trend for the globe necessarily means an upward trend for the globe’s hottest places. We will see more of this — probably very soon.