Climate is the average weather pattern for a place or an area.  Usually, it is the average for a period of 30 years.  Far too many mistake this for how the weather is for the moment.  This is behind the accusation against climate scientists for not considering normal variation.  Climate scientists in fact consider measured variation.  They don’t talk about the weather right now but statistical averages.

Another expression of the mix-up is to mistake the climate of other regions.  “Cold climate” becomes misunderstood as if it meant constant cold.  In the same way “warm climate” is mistaken for it being warm year-round.  Deserts are often misjudged as if they had constant heatwave.  The worst or the best season is treated as if it applied year-round.  Why would a narrow zone in the mid-latitudes be the only one having seasons?  I can’t help wondering how the borders of it would look.  Would the air temperature change by tens of degrees in just a few hundred yards?  I don’t think the laws of nature allows for that.  At least not for months to an end like the myths seems to presuppose.

The truth is that the entire world has some form of seasons.  Now, it does not necessarily have to be differences in temperature.  It can be difference in the amount of rain too.  Of cause it can vary how large these differences are.  Generally, it is coasts near the Equator which have the least seasonal variation.  The sea works like a buffer against changes in temperature.  The closer to the poles one comes the more it varies.  Places situated it the middle of the large landmasses have larger seasonal differences too.  The largest seasonal variation is found in parts of inland Siberia.  There it is hot in summer and nearly record cold in winter.

The chief cause of differences in temperature is difference in how high the Sun is.  The closer to the poles one get the lower the Sun is on average.  The sunrays then become more spread-out and don’t heat as much.  In addition comes differences in altitude.  Thinner air is worse at keeping heat which makes it colder higher up.  Also, winds and ocean currents matter.  However, they modify the general pattern in some parts of the world.

Differences in precipitation is determined by this combined with the Earth rotating.  The later stops air from getting strait between the poles and the Equator.  Instead six circulation cells form were the air rises and sinks.  There are three in the northern hemisphere and three in the southern one.  At the Equator air rises and creates a belt of downpours.  One third of the distance to the poles it instead sinks and makes these areas dry.  At two third of the distance the air tend to rise again.  This creates a more shifting and less intense belt of rain.  The air also sinks at the poles which make them dry too.  This is not as noticeable since they are so cold.

The differences in distance to the Sun are too small to create seasons.  Instead they are caused by the angle between the Earth’s axis and the plane of its orbit.  The Earth’s axis in not at 90 degrees to its orbit around the Sun.  It is 66½ degree and pointed towards about the same direction during a human lifetime.  Yearly variation arises in how high the Sun is.  Moreover, this creates differences in how long the Sun is up.  The result is a yearly difference in how much the Sun can heat.  The rain belts mentioned above move with the seasons.  Please note that the seasons are reversed in the northern and southern hemispheres.  A season in the northern hemisphere is the opposite one in the southern.

Seas vary less in temperature over the year then landmasses do.  In some parts of the world this creates seasonal differences in which one is the warmest.  This produce changes in air pressure making winds change direction.  Areas which would otherwise be dry get reliable rain in summer.  This is called monsoon and varies in strength.  Strongest it is in Asia because this landmass is the largest.

Around the Equator there are areas which are equally warm year-round.  The difference in the amount of rain there follows a double seasonal cycle.  This means two yearly peaks: one after each equinox.  A little further from the Equator are areas with rainy and dry seasons.  The rainy season is in the summer half of the year and gets proportionally shorter the further one comes.  At least if there is no monsoon.  Such an effect only occurs on the eastern side of the continents.

When the rainy season in summer disappears one reaches the deserts.  They almost always have a noticeable temperature difference over the year.  In the winter it is as such less hot than it is in the summer.  In addition there are large temperature differences between day and night.  Large parts have frosty nights in winter.  The deserts furthest to the poles can have months below freezing.  But I think not even they have snow that often in winter.  There can be years between the rains which then comes as cloudbursts.

Deserts can border to sea on the western side of the continents.  Otherwise they are surrounded in all directions by regions with more reliable precipitation.  In areas around the coldest deserts they get small amounts year-round.  In other places the precipitation can come in either the summer or the winter.  The later applies to areas towards the poles from hotter deserts.  On the west coast of the continents they can relatively quickly turn into regions with reliable rain.  This is called Mediterranean climate since the largest area is there.  These areas have tangible differences in temperature over the year.  In contrast it is rarely below freezing in winter.  The summers are dry and the winters are rainy.  Autumn and spring can be rainy to higher or lower degrees.

Moist areas in the mid-latitudes have four clear seasons.  Then I mean winter, spring, summer and autumn.  Getting below freezing in winter is common and usually leads to snow.  Which season has the most precipitation no longer matters much.  Instead it is temperature which determines the growing season.  The latter gradually decrease in length the closer one gets to the poles.  Eventually one reaches areas were the soil is constantly frozen.  Only the uppermost layer of the soil thaws in summer.  If this is too thin for trees to grow the area is covered in low plants.  These are the coldest areas having any vegetation at all.

Closest to the poles are areas where the temperature rarely or never reaches above freezing.  These are permanently covered in ice if they are not too windy.  In that case one gets a landscape of rocks and gravel.  This does not prevent the temperature from shifting considerably over the year.  However, as long as the snow does not melt away it is deposited and compressed into ice.  Such a layer of ice can grow up to 4 kilometres (2½ miles) thick.  The amount of snow gradually decreases the higher one gets.  Eventually an equilibrium is reached between accumulating and melting.  Is it too cold the latter is due to the ice moving towards the sea.  There it can float away and melt.

As I have previously explained temperature decreases by altitude.  Highlands can have an average temperature far below the lowlands’.  This creates vertical zones of colder and colder climate.  On high latitudes the difference is small to the climate closer to the poles.  But the higher one gets the more the temperature varies between day and night.  Getting closer to the Equator the zones move higher up.  This makes larger and larger differences between day and night on the mountains.  Close to the Equator day and night determines how warn or cold it is.  The differences in temperature over the year are too small to determine that.


Uploaded on the 17th of May 2024.