Climate explained: Sunspots do affect our weather, a bit, but not as much as other things



NASA

Robert McLachlan, Massey University


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Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz


Are we headed for a period with lower Solar activity, i.e. sunspots? How long will it last? What happens to our world when global warming and the end of this period converge?

When climate change comes up in conversation, the question of a possible link with the Sun is often raised.

The Sun is a highly active and complicated body. Its behaviour does change over time and this can affect our climate. But these impacts are much smaller than those caused by our burning of fossil fuels and, crucially, they do not build up over time.

The main change in the Sun is an 11-year Solar cycle of high and low activity, which initially revealed itself in a count of sunspots.

One decade of solar activity in one hour.

Sunspots have been observed continuously since 1609, although their cyclical variation was not noticed until much later. At the peak of the cycle, about 0.1% more Solar energy reaches the Earth, which can increase global average temperatures by 0.05-0.1℃.

This is small, but it can be detected in the climate record.

It’s smaller than other known sources of temperature variation, such as volcanoes (for example, the large eruption of Mt Pinatubo, in the Philippines in 1991, cooled Earth by up to 0.4℃ for several years) and the El Niño Southern Oscillation, which causes variations of up to 0.4℃.




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And it’s small compared to human-induced global warming, which has been accumulating at 0.2℃ per decade since 1980.

Although each 11-year Solar cycle is different, and the processes underlying them are not fully understood, overall the cycle has been stable for hundreds of millions of years.

A little ice age

A famous period of low Solar activity, known as the Maunder Minimum, ran from 1645 to 1715. It happened at a similar time as the Little Ice Age in Europe.

But the fall in Solar activity was too small to account for the temperature drop, which has since been attributed to volcanic eruptions.

Solar activity picked up during the 20th century, reaching a peak in the cycle that ran from 1954 to 1964, before falling away to a very weak cycle in 2009-19.

Bear in mind, though, that the climatic difference between a strong and a weak cycle is small.

Forecasting the Solar cycle

Because changes in Solar activity are important to spacecraft and to radio communications, there is a Solar Cycle Prediction Panel who meet to pool the available evidence.

Experts there are currently predicting the next cycle, which will run to 2030, will be similar to the last one. Beyond that, they’re not saying.

If activity picks up again, and its peak happened to coincide with a strong El Niño, we could see a boost in temperatures of 0.3℃ for a year or two. That would be similar to what happened during the El Niño of 2016, which featured record air and sea temperatures, wildfires, rainfall events and bleaching of the Great Barrier Reef.

The extreme weather events of that year provided a glimpse into the future. They gave examples of what even average years will look like after another decade of steadily worsening global warming.

A journey to the Sun

Solar physics is an active area of research. Apart from its importance to us, the Sun is a playground for the high-energy physics of plasmas governed by powerful magnetic, nuclear and fluid-dynamical forces.

The Solar cycle is driven by a dynamo coupling kinetic, magnetic and electrical energy.




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That’s pretty hard to study in the lab, so research proceeds by a combination of observation, mathematical analysis and computer simulation.

Two spacecraft are currently directly observing the Sun: NASA’s Parker Solar Probe (which will eventually approach to just 5% of the Earth-Sun distance), and ESA’s Solar Orbiter, which is en route to observe the Sun’s poles.

Hopefully one day we will have a better picture of the processes involved in sunspots and the Solar cycle.The Conversation

Exploring the 11-year Solar cycle.

Robert McLachlan, Professor in Applied Mathematics, Massey University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate explained: how white roofs help to reflect the sun’s heat



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Nilesh Bakshi, Te Herenga Waka — Victoria University of Wellington and Maibritt Pedersen Zari, Te Herenga Waka — Victoria University of Wellington

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Does the white roof concept really work? If so, is it suitable for New Zealand conditions?

Generally, white materials reflect more light than dark ones, and this is also true for buildings and infrastructure. The outside and roof of a building soak up the heat from the sun, but if they are made of materials and finishes in lighter or white colours, this can minimise this solar absorption.

During the warmer part of the year, this can keep the temperature inside the building cooler. This is especially important for building and construction materials such as concrete, stone and asphalt, which store and re-radiate heat.




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On a hot day, a white roof can keep the temperature cooler inside the building.
from http://www.shutterstock.com

A New Zealand study tested near-identical buildings in Auckland with either a red or white roof. It found that even in Auckland’s temperate climate, white roofs reduced the need for air conditioning during hotter periods, without reducing comfort during cooler seasons.

The study also identified several large-scale white-roof installations, including at Auckland International Airport, shopping centres and commercial buildings, but the effect was less clear.

This research suggests that there is potential for white-roof installations to significantly reduce the amount of energy needed to cool buildings. This would in turn reduce greenhouse gas emissions and also help us to adapt to rising temperatures.

It is difficult to quantify the impact for New Zealand’s housing stock because existing studies are mostly limited to larger commercial buildings. But research carried out so far suggests white roofs could be a viable approach to minimising the heat taken up by buildings during hotter parts of the year.

Cooling cities

White roofs can also help reduce the temperature of whole cities. Many city centres include large buildings made of concrete or other materials that collect and store solar heat during the day. In a phenomenon known as the “urban heat island” effect, city centres can often be several degrees warmer than the surrounding countryside.

When cities are hotter, they use more energy for cooling. This usually results in more greenhouse gas emissions, due in part to the energy consumed, and contributes further to climate change.

New Zealand is different because our land mass has a maximum width of 400 kilometres. This means that unlike many urban islands on the African, Asian or American continents, New Zealand’s city centres benefit from the cooling effects of being near the ocean.




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There are many international studies showing white roofs are effective in mitigating the urban heat island effect in densely populated cities. But there is little evidence that using white roofs in New Zealand cities could result in significant energy reductions.

A growing number of studies suggest making the surfaces of buildings and infrastructure more light reflecting could significantly lower extreme temperatures, particularly during heat waves, not just in cities but in rural areas as well. A recent study shows strategic replacement of dark surfaces with white could lower heatwave maximum temperatures by 2℃ or more, in a range of locations.

But studies have also identified some practical limitations and potential side effects, including the possibility of reduced evaporation and rainfall in urban areas in drier climates.

In conclusion, white roofs could be a good idea for New Zealand to keep homes and cities slightly cooler. As temperatures continue to rise, this could reduce the energy needed for cooling. We should consider this option more often, particularly for commercial-scale buildings made of heat-retaining materials in larger cities.The Conversation

Nilesh Bakshi, Lecturer, Te Herenga Waka — Victoria University of Wellington and Maibritt Pedersen Zari, Senior Lecturer in Sustainable Architecture, Te Herenga Waka — Victoria University of Wellington

This article is republished from The Conversation under a Creative Commons license. Read the original article.