Post No.: 0288
Many people don’t understand why, despite overall rising average global temperatures over the past several decades, or global warming and melting glaciers, we’re experiencing more extreme cold weather events, as well as hot weather events, around some places at the moment. Intuitions will fail to understand why the warmer the air is, the more likely we are to get heavy rainfall, thunderstorms, and even sometimes snow and icy hailstorms. Let’s investigate then…
When the atmosphere gets warmer, the seas and oceans evaporate more, and warmer air can also hold more moisture relative to colder air too (you’ll know this because it’s generally only ever humid if it’s also hot). Warmer air is more energetic and this greater energy and moisture held in the atmosphere leads to more heavy wet weather events, stronger winds, more instances of tropical storms, and if these air volumes travel to cold regions of the planet then it’ll mean extreme snowfall events there.
Hail are icy water pellets, and ice is normally freezing cold. For hail to form, it requires plenty of buoyant warm and moist air. Warm air is able to hold more moisture than cold air as stated before, so that’s one ingredient. Warmer air also rises relative to colder air (you’ll know this with hot air balloons), so this warm and moist air is lifted to the higher parts of the troposphere (the lowest region of the atmosphere), where it’s colder than the lower parts of the troposphere. Here, the moist water droplets can freeze and form icy water pellets. And the warmer the air is and the greater the power of the updrafts, the larger these hailstones can build up to be during thunderstorms because larger and heavier hailstones are able to be suspended in the air until they’re eventually too heavy for even these updrafts, by which time they’ll then fall onto the ground (and maybe smash into and damage property). Therefore increased cases of massive hailstorms in summers are as a result of global warming.
Thunderstorms occur more in the summer seasons, or more precisely during hot weather, because as warm and moist air cools as it rises, the water vapour condenses and forms clouds. Condensation releases latent energy, which helps storm, or cumulonimbus, clouds to grow. Eventually, these condensed water droplets and ice fall to the ground as rain – small particles of ice will melt into liquid by the time they hit the ground, while larger particles will fall as solid hailstones as above.
Also, in general, more warm and moist air will lead to more severe snowstorms and windy and icy weather in the winter seasons too. High-pressure areas of atmosphere meeting with low-pressure areas will create fronts that’ll in turn create winds where they meet. The strength of the wind depends on the size of the difference in pressure between these high and low-pressure regions, and the atmospheric temperature corresponds with the atmospheric pressure for a given volume of air. Thus the hotter these hot air masses get, when they meet colder air masses, the stronger the winds will be. (It’s like opening an exterior door when either the outside is hot and the inside is air-conditioned and cool, or the inside is heated and warm and the outside is cold – hence why large buildings use revolving doors.) And winds can contribute to the feeling of cold wherever there’s moisture too (try blowing on some dry skin, and then try blowing on some wet skin – the latter feels much colder).
Snow again needs moisture in the air, and when warm and moist air travels over to a colder region, rain or snow will fall. Also, regarding the polar jet stream in the Northern Hemisphere – as the Arctic air gets warmer, the now smaller differential between the relatively cold Arctic air above and warm continental or tropical air below this jet stream causes it to slow down, which causes it to take wild swings or dips. If this jet stream bends under a country then there’ll be more cold weather events, and if it bends over a country then there’ll be more hot weather events, there. So if it dips farther south than usual then that means the cold air will reach farther south to places that don’t usually experience Arctic conditions. These dips tend to hang around for a while too hence the weather we’ll get will hang around for longer i.e. both extreme cold and hot weather events become more frequent, or both floods and droughts last longer.
Lake-effect snow will also occur when there’s no longer ice on a lake (because of a warmer climate) hence there’s more evaporation from the lake, and more snow when this vapour rises and cools because snow needs to form from moisture held in the air. Thus we can get more snow this way when it’s warmer too.
Melting ice at the poles and warmer waters lead to rising sea levels. There are a few runaway effects or positive feedback effects, and tipping points. A tipping point is a point at which a series of small changes or incidents suddenly causes a disproportionately much larger change – it’s like metaphorically taking just one more step forwards and suddenly falling off a cliff edge, onto a new equilibrium with no straightforward return. And a positive feedback effect in science doesn’t necessarily mean a good thing but means the more something happens, the even more it’s going to happen because the causes and effects self-reinforce each other in a feedback loop i.e. it results in a runaway escalation, which is a very bad thing here because more warming will create even more warming.
The albedo effect is the way lighter-coloured surfaces reflect heat more whilst darker-coloured surfaces absorb heat more (you’ll know this when trying to sit on a black leather seat that’s been sitting in the summer sunshine for a while!) Snow and ice (ice sheets, ice caps and other glaciers) are white or otherwise relatively much lighter in colour compared to liquid water, land or algae, and so the less ice there is to reflect the Sun’s energy back out into space, the greater the global heat retention and therefore an even faster melting of icebergs and so forth, and the even more rapidly warmer the Earth will get. Forest fires within the Arctic, due to hotter summers there, may cover white snowy areas with a layer of dark soot too.
There are also a number of methane stores trapped within the ice along the Arctic, such as Siberia, and methane is a potent greenhouse gas (methane is, gram-for-gram, a far more potent greenhouse gas than carbon dioxide, although it doesn’t last in the atmosphere for quite as long) so if these gases get released into the atmosphere because of the melting ice, it could be a key point of no return.
Water vapour is actually a very effective greenhouse gas too (more so than carbon dioxide per weight), but the amount of water vapour present in the atmosphere is determined primarily by the temperature – thus it’s considered an important feedback mechanism of climate rather than a driver of it.
These runaway effects or tipping points mean that, even though we may think it’s okay now and we’ll cope with any gradual changes as we (sort of) have so far – well, these changes will quite likely suddenly accelerate one day. So even ‘just’ a 1 or 2°C increase will have potentially massive effects. A couple of degrees can make a big difference to the balance of entire ecosystems – in ecosystems or food chains, even if just one keystone fails then all the other parts will feel the effects of this directly or indirectly. (Many people even personally feel the difference between 18 and 16°C in a room, for instance, and will complain about it!) At the moment, we still have time to prevent meeting the cliff edge, but some predict that we only have about a decade to do so.
Plants and trees are supposed to balance out the atmospheric carbon – the more carbon in the air, the more trees grow – but not if we keep on cutting down the jungles and forests because of the food and things we want to buy(!) Burning them down and not letting them regrow contributes to another runaway effect too.
There’s also a ‘climate lag’. We’ve not yet experienced the full rise in temperature that’ll occur as a result of the greenhouse gases already emitted into the atmosphere, due to the thermal inertia of the oceans. The warming oceans directly affect marine life. Sea-level temperatures are already rising in many places across the world today and are causing coral bleaching and confusion for migrating birds and marine life. Carbon dioxide also combines with water to create carbonic acid, and this ocean acidification literally dissolves coral reefs, which are made from calcium carbonate. This affects the marine food chain. Therefore it’s hardly just about the atmosphere warming or just about the problem of carbon dioxide in the atmosphere. Once there’s damage caused by rising ocean temperatures and acidification on marine ecosystems, the oceans may take a very long time to recover i.e. once we go too far, it won’t be quick or easy to correct things again.
So a warming atmosphere leads to more extreme weather events and climate changes – hence ‘climate change’ is an accurate and honest description of what’s happening and isn’t a term that’s sitting on the fence. Inland deserts will be even more extremely dry, and more storms and flooding will mean more places will be extremely wet, or coastal areas will simply be submerged. Fires will be more frequent too. Food production for humans will therefore become more difficult and more people will become displaced as climate refugees, hence it’s not just about the cost to other innocent species of life if one only cares about humans. Meow.
It’s hard to say whether particular tropical storms, floods, heat waves and the like are due to anthropogenic/human-generated causes or would’ve happened anyway – but we can be more confident in saying that they’re overall more common and more extreme because of them. Many times now, almost at least once every year, we ask the question ‘is this extreme weather just a one-off or something we must get used to?’ We can’t keep attributing these extreme weather events as ‘freak one-offs’ because they’re not one-offs anymore(!)
Statements like ‘the highest temperatures or rainfall since…’ need to be read and understood with caution (unless ‘…since records began’) – a one-off outlier can remain the most extreme value for centuries thus mask a rising trend that doesn’t breach that extreme single value (e.g. simply stating ‘the wettest year since 1888’ may mask the fact that 1888 was a true, natural freak event and the fact that the past several years has seen a gradually rising trend of wetter years, even though each individual year since hasn’t broken that 1888 record). So it’s better to look at complete graphs of measurements over time rather than cherry-pick statistics – and when we do this, we can see that there’s a general trend of rising average global temperatures over time. This has been independently verified by a number of organisations, from NASA and NOAA of USA, the Japan Meteorological Agency and the UK Met Office. Individual weather events can vary from one day to the next but the climate is about the general long-term trend, just like a stock price can fluctuate from one day to the next but have a general long-term trend.
Therefore unless we more-or-less completely wean off fossil fuels (drilling for oil, fracking for shale gas, coal-fired power stations, petrol cars, etc.), it’ll create average global temperatures that humans as a species have never ever experienced before…
Meow. This kitten isn’t going to pussyfoot about it when talking about global warming – the time to act is ****ing now!