I Asked How Much Hotter It Has Got And Got Two Different Answers

I wanted to answer one question. How much hotter has the Philippines got?

I got two answers. Both from good sources. They do not match.

Two Weather Histories

Nobody measured the temperature everywhere, every day, since 1940. So scientists build a model of the whole atmosphere and run it backwards, using whatever measurements do exist to keep it honest.

There are two of these for the Philippines. Both from the same European weather centre. One is called ERA5, the other ERA5-Land.

For Manila, ERA5 says the average temperature is 27.69 degrees. ERA5-Land says 26.6.

That is a whole degree of disagreement about the present.

And on warming it gets worse. ERA5 says Manila heats up 0.122 degrees every ten years. ERA5-Land says 0.072.

Across the six cities I checked both ways, ERA5 warms 1.9 times faster than ERA5-Land.

So What Do I Do With That?

I could average them. That would give me one clean number to put in big type.

It would also be a lie. Averaging two numbers that disagree does not make you more right. It just hides that you do not know.

So every warming number on this page is a range. Somewhere between 0.072 and 0.25 degrees per decade, depending on the city and which history you trust.

What They Agree On

This is the useful part.

Every single city warmed. Both models. All 6 of them, no exceptions.

And when I stopped asking about slopes and started asking about records, the disagreement mostly went away. A hottest day is a hottest day. It does not care about a model's average being a bit high.

8 of the 9 cities set their hottest day ever in 2020 or later.

Only one is older: Baguio, up in the mountains, still holds its record from 1966.

Same for decades. 8 of the 9 cities had their warmest full decade in the 2010s.

The Number That Made Me Sit Up

I counted days hotter than 35 degrees.

In Laoag, up north, the 1950s had 0.3 such days a year. Basically none.

The 2020s have 30.99.

Manila went from 3.0 a year to 20.39.

Now — careful again. Counting days above a line depends on where you think the temperature is, and the two models are a degree apart on that. So the jump is real. The exact size of it, I would not bet on.

Rain Is A Whole Other Story

Temperature barely changes across the country. Rain changes enormously.

Baguio gets 3,171 millimetres of rain a year. Manila gets 1,543. More than twice as much.

But the timing is wilder than the total. In Laoag the wettest month averages 435 millimetres. The driest averages 16.

28 times more rain in one month than another. Tell someone Laoag gets a certain amount of rain per year and you have told them almost nothing useful.

One Honest Warning

These are not thermometers. They are models on a grid, and each square is about 25 kilometres across.

So "Manila" here means a 25-kilometre square near Manila. Which means I cannot tell you anything about cities being hotter than the countryside around them — the squares are too big to see the difference.

Our own weather agency has the real thermometer records. I could not reach their website from a script, so I did not use them. That is a gap, and I would rather say so than paper over it.