Tag: Physics

One of the numerous effects of a warming climate.

An article that I wanted to share with you!

There is no question that we are warming the world, and in my mind, there’s very little doubt that it is us older persons who are the cause. Take this chart, for example, where the effects of populations in the 1980’s – 2000’s had a dramatic impact on the worsening trend:

The reason for today’s post is to share an article that writes of the science of precipitation.

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THE PHYSICS OF PRECIPITATION
IN A WARMING CLIMATE

WRITTEN BY DR ASHLEIGH MASSAM

The scientific consensus on climate change is that atmospheric temperatures are rising and will continue to rise. Mean global temperatures are already 1˚C warmer than preindustrial times (relative to 1850–1900), predominantly due to human activity increasing the amount of greenhouse gases in the atmosphere (IPCC, 2018a). The 2020 Paris Conference of Parties (COP) agreed on the aim of a 1.5˚C cap on climate change-induced warming, although without rapidly introducing measures to reduce carbon and greenhouse gas emissions, global warming could easily go beyond this limit. 

In fact, the Intergovernmental Panel on Climate Change (IPCC) warns that even a mean global temperature increase of 1.5˚C will lead to an increase in the frequency and intensity of rainfall events. But what links a warmer climate to an increase in intense rainfall events? This blog post will explain the physics behind the changes to precipitation rates in a warming climate.

A SIMPLE OVERVIEW OF THE PHYSICS

Climate projections simultaneously warn of higher annual mean surface temperatures, higher rates of intense rainfall and more frequent intense rainfall events. The atmospheric moisture content increases with respect to a change in temperature – essentially, the warmer the atmosphere, the more water is held in the atmosphere, and therefore higher rates of precipitation can be expected.

This is explained by the Clausius-Clapeyron relationship between surface temperature and water vapour. According to the Clausius-Clapeyron relationship, atmospheric water content increases by between 6 and 7% per 1 °C. Therefore, even just an increase of 1.5°C could result in ~9% more water in the atmosphere, which could have a major impact on storm systems and subsequent rainfall.

Storm systems travelling across oceans will have an increased moisture content from water evaporated from the sea surface, forming a larger storm system and therefore more precipitation. JBA has recently discussed the risk of flooding from intensifying rainfall due to climate change and this will be explored in respect to storm systems later in this blog.

HOW PRECIPITATION IS FORMED

In meteorology, precipitation can be liquid or solid water that falls from the atmosphere and reaches the Earth’s surface. Types of precipitation include rain, sleet, or snow, depending on the temperature of the atmosphere. During the water cycle (fig. 1), water evaporates from the surface into the atmosphere, and changes state from liquid to vapour. The water vapour forms cloud droplets, which join together until the heavy droplets fall from the clouds as precipitation. Several processes affect this simple view of the journey from evaporation to precipitation.

Figure 1: A diagram of the water cycle showing the connections between water masses, the atmosphere and the transpiration and condensation of water vapour.

THE SURFACE TEMPERATURE – PRECIPITATION RELATIONSHIP IN MORE DEPTH

The connection between precipitation and surface temperature is defined by the Clausius-Clapeyron equations. The Clausius-Clapeyron equations calculate the energy required to cause a chemical reaction at a given pressure. In terms of precipitation, the Clausius-Clapeyron equations can be used to calculate the thermal energy required to condense water vapour into droplets when the atmospheric pressure is known. 

When water droplets are evaporated into the atmosphere, they travel upwards. As the Clausius-Clapeyron relationship is dependent on atmospheric pressure, the thermal energy requirement for a phase change is lower at a lower pressure. As the water droplets travel upwards, two things happen: 

  1. The atmospheric pressure decreases, and 
  2. The atmospheric temperature cools (this is known as the temperature lapse rate and is typically estimated at -6.5°C per kilometre). 

When the water vapour reaches an elevation where the atmospheric pressure and temperature satisfy the Clausius-Clapeyron relationship, the water vapour condenses into cloud droplets. 

IMPACTS OF A WARMING CLIMATE ON THE SURFACE TEMPERATURE – PRECIPITATION RELATIONSHIP

The release of carbon dioxide, and other greenhouse gases, into the atmosphere by humans has already led to climate change in the form of atmospheric warming. Long-term measurements show that the atmosphere has already warmed by 1°C since 1900. IPCC projections suggest that additional warming is inevitable, and attempts are being made to keep global atmospheric warming to under 1.5°C. Although, as previously mentioned, this could still increase the frequency and intensity of rainfall (IPCC, 2018b). To understand how an increase in annual mean surface temperature will influence rainfall events, we can apply the Clausius-Clapeyron relationship in a geographical context. 

As the Clausius-Clapeyron equations define the relationship between vapour and pressure, they can also be used to define the saturation vapour pressure with respect to temperature. In meteorology, the saturation vapour pressure is the maximum pressure of water vapour, at a given temperature, before it condenses. Therefore, the pressure required to condense a water droplet increases exponentially with respect to a change in temperature. 

This means that the Clausius-Clapeyron relationship can be used to determine the moisture content of the atmosphere. Warmer atmospheric temperatures will increase the atmospheric moisture content before condensation because the atmospheric pressure will not be affected by climate change in the same way as temperature. This results in the previously mentioned calculation that moisture content will increase by ~6.5% in the atmosphere per 1°C increase in temperature and means that atmospheric warming of 1.5°C will yield an increase in atmospheric moisture content of ~9%.

THE EFFECT ON STORMS AND PRECIPITATION

This ~9% increase has an impact on storm systems and therefore rainfall. Hurricane Harvey made landfall on the coast of Texas in August 2017. Over seven days, areas of Texas including Galveston and Houston experienced nearly 1.5 metres of rainfall. 

Research published since the event suggests that the intensity of Hurricane Harvey is attributable to a combination of the storm stalling over one location and climate change. The Gulf of Mexico, the source of moisture for Hurricane Harvey, has experienced anthropogenic-induced sea-surface temperature warming of 1°C since preindustrial times (Pall et al., 2017; Trenberth et al., 2018). Comparing Hurricane Harvey’s precipitation records with an equivalent event from 1950, extreme value analysis concluded that climate change contributed to a 5-7% increase in rainfall rates covering the full region affected by the hurricane (Risser and Wehner, 2017). 

With an increase in rainfall events and the wider impacts of climate change, it’s important for organisations to think about the potential risk to their business. JBA’s UK Climate Change Flood Model assesses and quantifies future flood risk in the UK under a warming climate and complements our range of global Climate Change Analytics, helping clients to understand and manage the effects of climate change on their assets and to enable long-term planning.

For more information on our climate change work, including bespoke consultancy services offered by our expert team, get in touch.

REFERENCES

IPCC, 2018a: Summary for Policymakers. In: Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I.Gomis, E. Lonnoy, T.Maycock, M.Tignor, and T. Waterfield (eds.)].]. World Meteorological Organization, Geneva, Switzerland.

IPCC, 2018b. Impacts of 1.5ºC Global Warming on Natural and Human Systems. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I.Gomis, E. Lonnoy, T.Maycock, M.Tignor, and T. Waterfield (eds.)]. World Meteorological Organization, Geneva, Switzerland.

Pall, P., Patricola, C.M., Wehner, M.F., Stone, D.A., Paciorek, C.J., Collins, W.D. 2017. Diagnosing conditional anthropogenic contributions to heavy Colorado rainfall in September 2013. Weather and Climate Extremes, 17, pp 1-6.

Risser, M.D., Wehner, MF. 2017. Attributable human-induced changes in the likelihood and magnitude of the observed extreme precipitation during Hurricane Harvey. Geophysical Research Letters¸ 44(24), doi: 10.1002/2017GL075888.

Trenberth, K.E., Cheng, L., Jacobs, P., Zhang, Y., Fasullo, J. 2018. Hurricane Harvey links to ocean heat content and climate change adaptation. Earth’s Future, 6(5), doi: 10.1029/2018EF000825

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The IPCC states what is clearly known in science circles; a warmer atmosphere equals more moisture in the air and that translates into more rainfall.

It comes down to warmer atmospheric temperatures increasing the atmospheric moisture content before condensation, simply because the atmospheric pressure will not be affected by climate change in the same way as temperature, as was described earlier in the paper. The reference to Hurricane Harvey was very powerful.

The world has to focus on climate change in an urgent manner. Because there isn’t a great deal of time, something like 10 years, at most, to bring about huge changes in the way we consume energy.

The mystery of telepathy

Just a bit more science about that sixth sense.

Yesterday, I wrote about how science was coming up with some pretty strong evidence that humans do have the ability to communicate in a way that might be called ‘telepathic’.

If (and that’s a big ‘if’) I have any understanding of the science, I believe it has much to do with quantum physics.  So I thought it fun to take a small diversion in today’s Post and give you some material on this very strange world of the very, very small.

From A Lazyman’s Guide to Quantum Physics,

What is Quantum Physics?

That’s an easy one: it’s the science of things so small that the quantum nature of reality has an effect. Quantum means ‘discrete amount’ or ‘portion’. Max Planck discovered in 1900 that you couldn’t get smaller than a certain minimum amount of anything. This minimum amount is now called the Planck unit.

Why is it weird?

Niels Bohr, the father of the orthodox ‘Copenhagen Interpretation’ of quantum physics once said, “Anyone who is not shocked by quantum theory has not understood it“.

To understand the weirdness completely, you just need to know about three experiments: Light Bulb, Two Slits, Schroedinger’s Cat.

Two Slits

The simplest experiment to demonstrate quantum weirdness involves shining a light through two parallel slits and looking at the screen. It can be shown that a single photon (particle of light) can interfere with itself, as if it travelled through both slits at once.

Light Bulb

Imagine a light bulb filament gives out a photon, seemingly in a random direction. Erwin Schroedinger came up with a nine-letter-long equation that correctly predicts the chances of finding that photon at any given point. He envisaged a kind of wave, like a ripple from a pebble dropped into a pond, spreading out from the filament. Once you look at the photon, this ‘wavefunction’ collapses into the single point at which the photon really is.

Schroedinger’s Cat

In this experiment, we take your pet cat and put it in a box with a bottle of cyanide. We rig it up so that a detector looks at an isolated electron and determines whether it is ‘spin up’ or ‘spin down’ (it can have either characteristic, seemingly at random). If it is ‘spin up’, then the bottle is opened and the cat gets it. Ten minutes later we open the box and see if the cat is alive or dead. The question is: what state is the cat in between the detector being activated and you opening the box. Nobody has actually done this experiment (to my knowledge) but it does show up a paradox that arises in certain interpretations.

To conclude I will offer this quotation reputed to be from the great master himself, Albert Einstein,

The more success the quantum theory has, the sillier it looks.

Beautiful minds; Hugh Everett

Two fascinating films about two very beautiful minds, Hugh Everett III and Stephen Hawking.

Hugh Everett III

A documentary on PBS entitled Parallel World, Parallel Lives traces in a deeply personal way, the efforts of the son of Hugh Everett, Mark Oliver Everett, to find out more about his father, who died in 1982, just 51 years old.  Mark Everett is an accomplished musician and much of his music makes it onto the soundtrack of the film. Here’s a brief extract from an article from Scientific American.

Hugh Everett III

Hugh Everett III was a brilliant mathematician, an iconoclastic quantum theorist and, later, a successful defense contractor with access to the nation’s most sensitive military secrets. He introduced a new conception of reality to physics and influenced the course of world history at a time when nuclear Armageddon loomed large. To science-fiction aficionados, he remains a folk hero: the man who invented a quantum theory of multiple universes. To his children, he was someone else again: an emotionally unavailable father; “a lump of furniture sitting at the dining room table,” cigarette in hand.

Here’s a taste of the film from YouTube.

But you may prefer to watch the whole programme, courtesy of Top Documentary Films.

A fascinating programme and one which shows great courage and bravery from Mark Everett in dealing with his memories and emotions about a brilliant but emotionally flawed father.

Thursday, Stephen Hawking.