Climate Change - The European Heatwave of June 2019

An unusually early and exceptionally intense heatwave set new temperature records in Europe.


The month of June was the hottest on record for the continent, with the average temperature 2° Celsius above normal.

"Every heatwave occurring in Europe today is made more likely and more intense by human-induced climate change," said a study published by scientists at World Weather Attribution .

Currently such an event is estimated to occur with a return period of 30 years, but similarly-frequent heatwaves would have likely been about 4 ºC cooler a century ago. 

In other words, a heatwave of this intensity is occurring at least 10 times more frequently today than a century ago.

The hottest summers in Europe in the last 500 years have all come in the last 17 years.

Climate Change - The Greenhouse Effect

What do scientists mean by the "Greenhouse Effect"?

When the Sun's energy arrives at the Earth, it travels through the air.

Some is reflected back to space, but some hits the Earth and warms it.

The warm Earth gives off infrared radiation with various wavelengths.  

Some of those waves can pass back out of the air to space, but some are absorbed by certain gases in the air.

The gases then re-emit the energy into the air.

If there are more of those gases, less heat escapes into space.

An extreme case has happened on Venus.

Concentrated 'greenhouse gases' on Venus have caused the surface temperature to rise to 735 Kelvin (462 degrees C; around 900 degrees F) - this is not going to happen on Earth.


Carbon dioxide levels in the atmosphere have risen quickly since people began burning large quantities of fossil fuels.

There was carbon dioxide in the air before that, at around 270 parts per million.

Without any carbon dioxide, the Earth would be very cold.

The temperature would be around -18 degrees C.

There have been times when most of the carbon dioxide was trapped in rocks.

The Earth cooled into a state called 'Snowball Earth'. 

These ancient events are unlikely to be repeated - they occurred when the Sun was producing less energy.

Climate Change - The Carbon Cycle

Carbon dioxide is always in the atmosphere as part of the Earth's carbon cycle.

The global carbon cycle transfers carbon through the Earth’s different parts - the atmosphere, oceans, soil, plants, and animals. 

So carbon moves around — it flows — from place to place.



Carbon dioxide (CO2) is the main greenhouse gas emitted through human activities. 

Human activities are changing the carbon cycle.

First, by adding more CO2 to the atmosphere, mainly by burning fossil fuels.

Also by changing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. 

Human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution. 

The carbon sinks, on land and in the oceans, have responded by increasing the amount of carbon they absorb each year.

Carbon sinks cope with about half of human greenhouse gas emissions. 

The other half has accumulated in the atmosphere.

Daniel Rothman, Professor of geophysics in the MIT Department of Earth, Atmospheric and Planetary Sciences and co-director of MIT’s Lorenz Center, has identified “thresholds of catastrophe” in the carbon cycle that, if exceeded, would lead to an unstable environment, and ultimately, mass extinction.



The diagram above shows a comparison of the current mass of all life on Earth with the amount of carbon that humans have added to the atmosphere since 1870. Humans have now burned through the equivalent of an entire biosphere.

Climate Change - Iceland

Iceland lies on the Mid-Atlantic Ridge, which is why it has volcanic activity.





Iceland also has ice caps and glaciers.

Iceland is one of the fastest-warming places on the planet – as much as four times the Northern Hemisphere average. 

The glaciers that cover more than 10 percent of the island are losing an average of 11 billion tons of ice a year. 

      

  

Guides work to build a new bridge across a river draining from Falljokull glacier ahead of the summer season when meltwater run-off increases [Alexander Lerche/Al Jazeera]

The water melting from Iceland's glaciers would fill 50 of the world's largest trucks every minute.

Parts of Iceland are rising as the ice caps melt, reducing the weight on the Earth's crust.

The thinning of the ice caps reduces the pressure on the rocks.

Geologists know lower pressure from above makes volcanoes erupt more easily.

Lower pressure allows volcanic gases to expand, and mantle rocks melt more easily at lower pressure as well.

So more magma can rise into the volcanic systems.

As that happens, Iceland's volcanoes may get more active.

Climate Change - The Pliocene Rebooted?

Atmospheric carbon dioxide concentration is now over 400 parts per million (ppm).

It last reached similar levels during the Pliocene, 5.3-2.6 million years ago.

 Outcrop of Middle Pliocene diatomaceous lake beds at Ledi Geraru, northern Afar region of Ethiopia. (photo: Roy Johnson.)

In the middle Pliocene, the concentration of carbon dioxide in the air ranged from about 380 to 450 parts per million. 

During this period, the area around the North Pole was much warmer and wetter than it is now.



Summer temperatures in the Arctic were around 15 degrees C, which is about 8 degrees C warmer than they are now.

Global average temperatures were 2-3°C warmer than today.

Sea level was up to 40 metres higher than now.

Of course, there were no modern humans at that time.



Hominids of the Pliocene

Nor was there a global system of food supply relying on stable climates for agriculture.

For more on research into the climate of the Pliocene, and what it can tell us about the likely effects of 400 ppm CO2, "Science News" has a very good article.  

Another paper: "Pliocene and Eocene provide best analogs for near-future climates" - Burke et al, 2018 makes these points:

"We are effectively rewinding the climate clock by approximately 50 million years,reversing a multimillion year cooling trend in less than two centuries."

 "by 2030 CE, future climates most closely resemble Mid-Pliocene climates, and by 2150 CE, they most closely resemble Eocene climates."

Climate Change - Oceania

Oceania is a region made up of thousands of islands throughout the Central and South Pacific Ocean. 

It includes Australia, the smallest continent in terms of total land area.

Many of the nations in Oceania are Small Island Developing States (SIDS).

Many scientists say that Oceania is more vulnerable than most parts of the Earth to climate change, because of its climate and geography. 

The heavily coastal populations of the continent’s small islands are vulnerable to flooding and erosion because of sea level rise. 

An international team of researchers has produced this graph of ocean levels, for a period of time going back to around 500 BC. 

Five of the Solomon Islands have been swallowed whole by rising sea levels between 1947 and 2014. 

"It’s a perfect storm,” says Simon Albert of the University of Queensland. “There’s the background level of global sea-level rise, and then the added pressure of a natural trade wind cycle that has been physically pushing water into the Western Pacific."

Albert and his colleagues analysed aerial and satellite images from 1947 to 2014 to study the effects of creeping sea levels on the coastlines of 33 reef islands in the Solomons.

Five islands present in 1947, ranging in size from 1 to 5 hectares, had completely disappeared by 2014.

Another six islands had shrunk by 20 to 62 per cent in the same period, confirming anecdotal reports of people living in the area.

The most populated of these, Nuatambu Island, is home to 25 families, who have witnessed 11 houses wash into the sea since 2011.

Fiji’s shoreline has been receding about 15 centimetres per year over the last 90 years.

Samoa has lost about half a metre per year during that same time span. 

The global sea level graph is from this paper: 
"Temperature-driven global sea-level variability"

Climate Change - The Australian Heatwave of December 2019

Eucla, in south-east Western Australia, hit 49.8 degrees Celsius on December 19th, 2019.



The map shows Australia coloured dark red, indicating temperatures around 40°C. However, some spots of the country are covered with white spots, indicating the heat was inching towards 50°C.

Leading climate scientist Stefan Rahmstorf said.....

"the probability for this extreme heat occurring by chance in a world without global heating is essentially zero. "

Huge bushfires swept through many areas, destroying homes and wildlife.

It is estimated that around a billion animals died.

Another leading climate scientist, Michael Mann, said ...

"Yes -we might have still seen an Australian heat wave, but we wouldn't have seen such a RECORD early summer heatwave in the absence of human-caused planetary warming..."