Weather gone wild: will summer ever return?
Here’s how things look in the long term: summers will become dramatically more
rainy and winters in northern Croatia could feature much more precipitation,
writes Tanja Rudez.
20 September 2014
A friend from Berlin tells me they had a sunny and warm August there. Another
friend came over from Amsterdam. When he was welcomed by rain, he
concluded that the climate in Zagreb is changing, and becoming more like the
oceanic climate over there, with mild winters but also colder summers with
plenty of rain. My colleague who is normally a music critic said to me over a
morning coffee while we were talking about potential topics for the magazine,
‘I’ve concluded that Norwegian meteorologists give the most accurate weather
forecasts for this region. Those weather forecasts are being followed by many of
our people now. Norwegian forecasts are more accurate than those given by the
state meteorological department, or those you can find on Yahoo,’ claims the
music critic.
The weather this summer was amongst the hot topics: not only did it worry
people working in tourism and the finance minister Lalovac, who struggles to fill
up the budget, but the voluminous rains have also made everyday life more
difficult for us, ordinary mortals. Following a very mild winter and in many areas
a record warm period of three months, we were all hoping for a long, dry and hot
summer, which was hinted at by the long-term weather forecasts. But the
opposite happened. Voluminous rains, which flooded Slavonia in May, continued
falling throughout summer and especially for the first 15 days of September. So
they caused a new wave of floods across Croatia. ‘What happened to the
summer?’ asked many, and in the media and social networks a series of
discussions started about climate change. Of course, once again there was a
resurrection of unavoidable prophets of the arrival of the new ice age.
Age of extremes
‘Extreme precipitation over the past 6 months, as well as the record warm
winter of 2014, are the consequence of ever more frequent so-called blocking
synoptic situations in the atmosphere. A blocking situation means that a certain
sample of extreme deviations from the average happens over a significantly
longer period than before. A blocking situation is more frequent because of
stronger meridional energy transfer, and the transfer is stronger because of the
warming of the atmosphere. This means that these extremes are a direct
consequence of climate change,’ explained Dr. Ivica Vilibic, a professor at the
Institute for Oceanography and Fisheries in Split.
‘It is interesting that certain extremes are usually happening in a limited area so
that these floods are limited to an area of a radius of around 1,000 or a little bit
more kilometres, while in other parts of Europe and the world there is a
completely different situation. For example, our winter of 2014 was extremely
warm, while in the middle and eastern USA it was extremely cold. The winter of
2012 was renowned for a record snowfall in Dalmatia while at the same time it
was one of the warmest in the USA, etc. The strengthening of the blocking
situations in the atmosphere and the associated extremes are a direct
consequence of climate change,’ added Vilibic. Similar opinions are shared by
Professor Mirko Orlic from the Geophysical Department of the Natural History
Faculty in Zagreb. ‘For the huge amounts of rain that have been falling over the
past few months, we can blame global warming. Despite the warming on earth
being global, it is not equally distributed over all parts of the planet. The
warming is stronger in the polar areas, especially around the Arctic, compared
with around the equator. Because of this, there are changes to the atmospheric
circulation and the consequences of that are temperature disorders, which are
becoming larger and longer,’ Orlic said. ‘We had cyclones during the summer
before, and they would pass quickly, but now they are slower and come for
months. At the same time, while we have loads of rain, California is facing the
biggest drought in a hundred years. Winters are, on the other hand, reversed. In
our country, winter was very warm and with practically no snow, while if you
take for example Canada, where they usually have severe winters, it was
unusually cold,’ added Orlic, who was one of the reviewers for the fifth climate
report of the Intergovernmental Panel on Climate Change (IPCC).
Sea level rises
Orlic, together with Dr. Zoran Pasaric, authored an article about sea level rise,
one of many works which formed the basis of the IPCC report. That international
organisation, which gathers around 3,000 scientists from around the world, was
established in 1988 by the United Nations and the World Meteorological
Organisation. At that time, many scientists from around the world started
warning about global air temperature rising, which they linked to human
activity, especially the greenhouse effect. In nature, there is a process similar to
the one in a greenhouse: carbon dioxide, methane, nitrogen oxides and other
gases in the atmosphere soak up warm radiation and direct it towards earth.
Without those gases, life in its current form would be impossible. For example,
with a reduction in the amount of carbon dioxide in the atmosphere, Earth would
be inhospitably cold, a bit like Mars (minus 20 degrees celsius). If that gas
dominated the atmsophere, our planet would be like Venus, reaching a mindboggling 500 degrees celsius.
Nevertheless, the natural greenhouse effect has been strengthened through
human activity, so that since the beginning of the Industrial Revolution, the
amount of carbon dioxide in the air grew from around 280 ppm (ppm - the share
of greenhouse gases in a million molecules of dry air) to around 400 ppm, which
is a rise of 43%. Over the last hundred years, global air temperature grew by
around 0.8 degrees celsius, and the main part of that rise, 0.6 degrees celsius, has
happened since the 1950s. Also, in the last hundred years, the global sea level
rose by around 17 cm.
Changes in Greenland
‘Both the air temperature and the sea level rise have accelerated over the past 50
years. According to a new fifth report, a bigger part of the warming from the
middle of the twentieth century can be attributed to human activity, with a
probability of more than 95%. Given that the previous IPCC report had this at a
lower probability of around 90%, the conclusion is that today we can say with a
higher certainty that humans have an affect on climate,’ Orlic explained.
‘When we talk about the future, in the case of a doubling of the concentration of
greenhouse gases, we expect a further rise in temperatures ranging from 1.1 to
2.6 degrees celsius. Such a warming will be accompanied by a rise in sea levels
ranging from 32 to 63 cm. The temperature projections are very similar to those
we’ve seen in the previous report, but the projections for the sea level rise are
higher than before, the reason being that the new report took into account larger
changes in the dynamics of Greenland and Antarctica, which have been explicitly
excluded from previous reports,’ said Orlic.
The IPCC climate reports are an important basis for political negotiations at state
level about reductions in carbon dioxide and other greenhouse gas emissions.
This respectable international organisation, together with former American vicepresident Al Gore, won the 2007 Nobel Peace Prize.
But the IPCC has faced several scandals, the most serious of which was
Climategate. In November 2009, ahead of the climate conference in Copenhagen,
hackers published on the internet more than 1,000 private e-mails from IPCC
climatologists. Some of the hacked e-mails were represented in public by climate
sceptics and those who deny global warming as proof that the data had been
manipulated. Nevertheless, several independent scientific investigations not only
cleared the IPCC’s climatologists from accusations of scientific misconduct, but
also confirmed their studies about the dangers of global warming. But that
scandal helped strengthen climate sceptics and those who say we are facing
global cooling, even a new ice age.
Slowed down warming
Mirko Orlic points out that the IPCC does not shy away from controversial topics
such as the slowdown in warming we’ve seen since 1998, which was one of the
warmest years in the last 150 years.
‘First of all, I have to highlight that there was no cooling, only a slowing down of
the speed of the rise in temperature. That is not surprising, as this happened
twice before since we’ve been continuously following air temperatures. The first
time was at the beginning of the twentieth century and the second time in the
50s and 60s. One of the explanations is that this is a natural cycle with a
periodicity of 60 years, and we are now in that phase,’ Orlic explained.
‘In the IPCC’s report summary, it says that there was a slowdown of warming
because of three factors: a natural process with a periodicity of 60 years, a fall in
the intensity of solar radiation, and an increased amount of aerosols in the air
because of volcanic emissions. But greenhouse gases continued growing and
when, in some 10-20 years, the natural cycle ends, the warming will speed up
once again,’ highlighted Orlic, who thinks the average man often has the wrong
perception of global warming.
‘Some people think that with global warming, every day will be warmer, and that
there won’t be any seasons, but as long as the Earth’s axis is tilted, there will be
seasons,’ Orlic said.
The perception of space
‘Furthermore, people have a problem with perceiving space and time. Global
means for the entire world, so if we had a summer that was extremely wet and
cold, in many other countries it was extremely dry and hot. Furthermore, in
climatology we speak about 30-year averages. So, if in 30 years we face 20 dry
and 10 wet summers, the average is still dry, not wet,’ Orlic added.
As far as the future climate in Croatia goes, Orlic highlights that simulations point
towards rising temperatures, but the warming won’t be equal throughout the
year. ‘The warming should be strong during the summer and less pronounced in
winter. There will be dramatically less precipitation in the summer, but northern
Croatia will see much more precipitation than now.’
Ivica Vilibic also thinks that the scenario of a new ice age is impossible unless
there is an eruption of a supervolcano or an asteroid impact. ‘Global cooling is
impossible so long as people affect the atmosphere by releasing greenhouse
gases. If we stopped doing that now, the warming would continue for some time
to come because of a delay in the system. But locally it is possible for climate to
be cooler.’
Climate simulations
‘Someone might think that this could happen in the Mediterranean but all
climate simulations and measurements so far point to the fact that in our region
the temperature increase will be higher than global warming, and that the
frequency of so-called flash flood events, especially pronounced precipitation
extremes, will be higher in the future climate,’ said Ivica Vilibic.
‘This, of course, is a challenge for everyone who should be defining and
implementing adaptation and mitigation measures.’ Vilibic thinks that in the
future we will have to adapt to extreme weather in various ways. ‘Solving the
problems that come with extreme weather should be homework for society and
responsible agencies. Some agencies are working on it, because things are
moving at the European level. For example, the state meteorological institute has
introduced a system of warnings about extreme events in the last few years, a socalled meteoalarm,’ says Vilibic.
‘But some agencies are not working: for example, we should ban building on
potential landslide areas and floodplains, and we should have plans for extended
dry periods and heatwaves. Let’s just remember that a few years ago we almost
had a drying out of water that was supplying the whole of Istria. We were very
close to a catastrophe. We were saved at the last moment by rains, which might
not happen in the future,’ concluded Vilibic.
[Infographic: What happened this summer and did we ever have this much rain?
Map of Croatia with data explaining weather trends]
Meteorologist Dunja Placko-Brsnak on the accuracy of weather forecasts
We are getting warmer autumns and winters but with a lot of precipitation.
We cannot give an accurate long-term forecast. We forecast the trends.
How do weather forecasts come about in our area? The weather forecasts are
done based on prognostic models, coming mainly from two sources: the global
model of the European Centre for Mid-range Weather Forecasts (ECMWF) in
Reading in England and local model Aladdin, developed through the
collaboration of several European meteorological agencies, including ours. The
starting parameters of the model are the measured data collected from stations
from around the world and data from meteorological satellites, radio sonar data
from meteorological balloons, data from boats and buoys, radar data, etc. Based
on analysis of the current state of the atmosphere using measurement data,
results of the prognostic models and knowledge of the physical processes that
happen in the atmosphere, a forecaster creates a picture of the current and
future state of the atmosphere and expected changes and based on that they
make the weather forecast. Very short forecasts (up to 2 hours ahead) are based
on satellite and radar data and prognostic products available in real time, based
on which we can judge the movement and development of weather systems such
as clouds.
Global models: how accurate are weather forecasts?
The accuracy of short-term forecasts is great: around 90%. As far as longer-term
forecasts go, the reliability is smaller, and dependent on the state of the
atmosphere. With unstable weather, short-term forecasts are the most reliable.
Atmospheric processes are then very intense, happen in a relatively short time,
and are local in character. For a longer time period, a global model over some
areas gives a synoptic situation that determines the type of weather.
What is the reliability of monthly and seasonal forecasts?
Monthly and seasonal forecasts are built for special users and the interpretation
of those forecasts is different from the usual forecasts for shorter time periods.
With such forecasts, we cannot say what the weather will be like, for example, in
25 days’ time, but we look at deviations from some prognostic parameter
(temperature, rainfall) with respect to the average value over a certain time
period. So we forecast a trend, or in other words, whether we expect warmer or
colder than average weather, or if we expect it to be rainier or less rainy than
average. Such forecasts are given with associated probabilities (small, medium
and high) and are not very useable in everyday life. It is difficult to speak about
the reliability of such forecasts because they might say that a month will be
warmer than average when in reality you have two weeks of colder weather and
two weeks of warmer weather. Such a forecast would be correct, but surely in
the first two weeks you will hear users commenting that it was a bad forecast.
This is one of the reasons why such forecasts are not intended for the public.
Who to trust
What are the first seasonal forecasts for the coming autumn and winter?
During September, we did a forecast for the period of October to December 2014.
According to this, the average monthly temperature is forecast to be higher than
average, with a high probability. As far as precipitation goes, we forecast around
average or slightly above average with a medium probability. So, according to
the long-term forecast, we have ahead of us a relatively warm period, with
continuing above average precipitation possible. Of course, let’s bear in mind
that this is a long-term forecast for the whole of Croatia.
Over the last few months in Croatia, weather forecasts from Norway have been very
popular and many people claim that they are more reliable than local ones. What
do you say to this?
I too hear mentions of the Norwegian forecasts, but my experience is not so
exclusive. That is to say, this forecast is also the result of a global model for midterm forecast of weather, ECMWF, so the source is the same, but probably some
details have been added. But I’m not an expert in model development, so in fact I
don’t know what this is all about.