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Comment by theferalrobot | Hacker News Reader

Genuine question: Isn’t global warming supposed to cause more rainfall?

It’s expected to change the distribution of precipitation.

So more rainfall globally but possibly less in some regions? Do we know why that is exactly instead of just generally more rain?

Rainfall will be different. There will be more or less rain, at different times of the year, with a changed susceptibility to droughts and/ or floods. So yes, there may be more rain overall but - just as some places may get cooler - local climatic changes will be in multiple directions on multiple axes.

It won't be a smooth change to the new conditions either; there will be centuries of instability and infrastructure and agriculture will have to adapt to obsolescence every few decades.

I'm not a climatologist but I do know some of the reasons why:

The thermal gradient between the equator and the poles (a major driver) will weaken - the poles will heat up more quickly.

Ice at the poles drives some ocean currents.

Temperatures at different heights in the atmosphere will be affected differently.

Increased evaporation from oceans but higher ambient temperatures will change cloud formation unevenly.

Nights will cool down more slowly due to the 'blanket' effect of CO2.

The overall effects are interconnected of course, which is why there is so much work on modelling and so much work still to do.

Edit: I forgot to mention the effects on vegetation and landscape that will also feedback unevenly into the climate. e.g. rainforests depend on and generate a lot of rain; a rainforest may hit a tipping point where it is no longer viable and rainfall will then collapse over a large area.

If you're curious to learn more about this, I really strongly recommend reading the latest IPCC Assessment Report Summary for Policymakers[1]. It's a pretty easy read, will take an hour or two, and you'll come out the other side with a really good understanding of the fundamentals.

[1] Here's the latest, from AR5 in 2014. It's a little out of date, but it holds up fine as an introduction (mostly what's new since then is "we've done nothing, so things are now even worse"). AR6 is due out in 2022. https://www.ipcc.ch/site/assets/uploads/2018/02/AR5_SYR_FINA... (3.5 MB)

To add to the other poster - the type of rainfall will change as well. There is an appreciable difference between the spring showers we used to get that rained 2 or 3 inches over a 12-14 hour period, and the gully washers we have gotten in the last five to ten years locally that drop 1/2 to 1 inch in an hour or less.

Hotter air can hold more water. In cooler climates, the air over a region will become saturated with moisture, causing precipitation. In warmer climates, the air is able to hold a lot more water before becoming saturated, therefore the rain falls somewhere else.

I imagine you'll get more rainfall over oceans; air currents over land will hold onto moisture until they blow over oceans, cooling them. I also imagine you'll get more rainfall on the sides of mountains which are already regions where warm, damp air rapidly cools causing precipitation.

Please don't take this as truth, I'm just theorizing, I'm not qualified.

> Please don't take this as truth, I'm just theorizing, I'm not qualified.

Any climate conversation in a nutshell.

It's a loaded term really. Global warming is umbrella term for 'Extreme Weather Conditions'.

You get mega droughts followed by mega flooding (depending on region).

Those are tied to global increase in mean temperature.

None of this is actually true. Rain patterns are driven by ocean currents. And oceans are driven my Multi-decadal oscillations. Shifts in rain patterns due to these oscillations have always occurred.

Not sure what you mean by that. The number and severeness of natural disasters is only increasing[0].

Shifts in rain patterns due to these oscillations have always occurred, what does this mean?

[0] https://ourworldindata.org/grapher/number-of-natural-disaste...

It says number of "recorded" natural disasters. Do you really think there was only 6 natural disasters in 1920 in the whole world or is this data set a function of a time when the world was not: 1) interconnected by weather satellites and radios 2) globalized with regards to trade and 3) had open data and sharing between governments and standards for reporting on them

That means climate change is a natural function going back billions of years. See:

https://www.sciencedirect.com/topics/earth-and-planetary-sci...

Here's hurricane data in US going back to 1800s: https://www.aoml.noaa.gov/hrd/hurdat/All_U.S._Hurricanes.htm...

(Note, we didn't have instrumentation for measuring exact strength of hurricanes prior to satellite era in the 1970s)

It feels like you care strongly about it.

So I am sorry chrisco, but I am not sure what you are alluding to?

Yes, have always occurred. But now it's amplified due to other effects, partially (or primarily) driven by effects of global warming.

It's not the absolute we have to watch out for. It's the rate of change!

> Global warming is umbrella term for 'Extreme Weather Conditions'

Yes and no. It explicitly means that the average temperature, globally, is increasing. Drastically so.

Extreme weathers is just one of the side effects. Others include: ecological collapse, insane scale population migration, catastrophic sea level rise, etc, etc.

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