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Nowadays, everyone talks about it: climate change, and more importantly, how to stop it from happening. Although there's a lot of debate around the topic, the consensus is that by inventing a way of generating clean energy, we can slow down (and maybe even reverse) the effects global warming has on the planet. Using energy that was created without burning millions of years worth of stored carbon, we can not only power our everyday lives, but also capture the carbon we've been blowing into our atmosphere using the energy-intensive process of carbon capture and sequestration (CCS).

But there are still some problems. Currently, photovoltaic cells are pretty much useless during winter when it comes to fueling the homes of millions (at least where I live). We want to warm our homes, but there's not enough clean energy during those months, so we fall back on nuclear.

Wouldn't it therefore be better to have a small rise in global temperature?

  • A higher temperature means you don't have to warm your home during winter (as much).
  • During summer, you can use the extra energy generated by the photovoltaic cells to power air conditioners in order to cool buildings and
  • Use some excess energy to stop the runaway greenhouse effect using CCS.

Even though cooling requires more energy than heating, might it break even? Will the rise in temperature have a positive effect on our energy production and the ability to satisfy energy demand?

  • Welcome to Sustainable Living! I like your question, but one counter-argument is that photovoltaic cells have higher efficiency when it's cold. Nevertheless it would be interesting to see if overall the reduced efficiency in the summer outweighs the reduced need for heating (and extra air-con). – THelper Jul 23 at 14:42
  • According to this paper, the small increase in temperature won't make such a big difference in efficiency. – TVASO Jul 23 at 14:47
  • I am not expert, but we also have to put in the table the other consequences of climate change: summers more hot and winters more colds, and that makes us use more airconditioners and more heater, increasing our energy consumption and so on... – Antonio Veneroso Contreras Jul 23 at 16:50
  • Another factor is that a warmer atmosphere is able to carry more moisture, potentially resulting in more cloudy days and reduced solar PV output over the course of the year (especially with the reduction in efficiency that occurs at higher temperatures) – John M Nov 8 at 20:48
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tl;dr -- For the west coast of the U.S., a 20% decrease in heating demand and 18% increase in cooling demand results in a 5% reduction in carbon emissions from electricity and natural gas usage

Here's the approach I came up with to try and answer this question with some hard data.

1. Find a region of the U.S. which had a cold winter and mild summer, followed by a mild winter and a hot summer.

This is the sort of change we'd expect to see with global warming. If we look at the data for consecutive years, we minimize the effects of changes to the grid and/or population.

The U.S. Energy Information Agency publishes monthly regional data for heating and cooling degree days as part of the short term energy outlook.

Looking at data for all regions, I determined that 2013 to 2014 for the Pacific region best meets the criteria. The area includes Alaska, Washington, Oregon, California, and Hawaii. This area stretches pretty far from north to south, so makes a decent sample that we could use to extrapolate. From 2013 to 2014 this region experienced:

  • 20% increase in cooling degree days (= more energy needed for cooling)
  • 17% decrease in heating degree days (= less energy needed for heating)

enter image description here

The population in this region grew by slightly more than 1% over that time period, so likely not a huge factor in any changes in energy usage:

               2013         2014    % change
Alaska         735,132     736,732  
California  38,332,521  38,802,500  
Hawaii       1,404,054   1,419,561  
Oregon       3,930,065   3,970,239  
Washington   6,971,406   7,061,530  
            51,373,178  51,990,562    1.2%

2. Determine total usage of electricity and natural gas for heating over that time period

EIA provides monthly natural gas consumption by state. This is broken down by end use, so I looked at residential and commercial uses, which would predominantly cover heating. I left out use by vehicles and industry. Some industry uses would include heating, but for all five states this usage was fairly consistent month-to-month, and less than either residential or commercial usage for most months.

EIA also provides monthly generation by fuel source by state (scroll to "Generation" then "State-level generation and fuel consumption data" then "Monthly (back to 2001)") .

Here's a chart showing degree days (left axis) and energy for heating and electricity (right axis) using the above data sets:

enter image description here

3. Compare changes in heating, electric generation, and associated CO2 emissions

Here's a chart comparing 2013 and 2014 usage for the largest sources:

enter image description here

And here's the data summarized in a table with emissions data and percent change calculated:

                                    2013        2014       % change

Heating degree days                   3,365        2,776    -18%
Cooling degree days                     890        1,069     20%

Heating natural gas (MWh)       291,012,539  256,759,857    -12%
CO2 emissions (metric tons)      54,613,680   48,185,555    

Coal generation (MWh)            26,701,933   25,562,047     -4%
CO2 emissions (metric tons)      27,235,971   26,073,288    

Natural gas generation (MWh)    297,462,431  289,771,833     -3%
CO2 emissions (metric tons)     133,858,094  130,397,325    

Hydroelectric generation (MWh)  273,042,255  263,321,494     -4%
Nuclear generation (MWh)         52,745,666   52,966,598      0%
Solar generation (MWh)            7,708,892   19,940,312    159%
Wind generation (MWh)            55,861,453   58,717,774      5%
Other generation (MWh)           68,296,211   67,585,528     -1%
Total electric (MWh)            781,818,840  777,865,587     -1%

Total CO2 (metric tons)         215,707,745  204,656,168     -5%

Conclusion

This is a pretty limited (and possibly spurious) analysis, but it supports your hypothesis: a warmer climate reduces energy needs in the winter by a greater factor than the summertime increase.

The really interesting thing, especially in a U.S. context, is that a huge proportion of natural gas is used for heating in the winter. But in the summer, electricity from cooling comes from a more diverse set of sources. So any reduction in heating demand necessarily reduces CO2 emissions, but as the grid adds more wind and solar, increases in cooling demand don't necessarily increase CO2 emissions.

Some caveats to this:

  • Much of the population of California is on the southern coast, where heating and cooling demand is already limited due to the mild climate
  • None of this accounts for changes in population, economic activity, policy, or precipitation
  • Electric usage is for all uses (not just heating/cooling) so doesn't account for any economic factors
  • California added A LOT of solar, and some wind, during this time period, which contributed to the overall reduction in CO2 emissions from the electric sector
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Wouldn't it therefore be better to have a small rise in global temperature?

No. The radiative forcing by carbon dioxide does not increase solar radiation that can be captured by solar cells. The warmer temperatures actually decrease solar cell output, because solar cells really like cold temperatures and lots of radiation. You can't have both optimal temperature and optimal radiation at the same time, because solar radiation causes the temperature to increase.

If we could somehow manage radiative forcing, to reduce worldwide temperatures, we could make more power with solar cells.

Edit: Nice to have unexplained downvotes after an upvote. So, let me add some sources:

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The US isn't the only land mass in the world you know. In much of Africa people and animals are dying in the heat. And on a global scale the man made energy requirements are rising exponentially because of global warming. In Britain for instance people are busy installing air conditioning which they never needed before. If you even looked at the extra air conditioning installed in the US you would probably find it outweighs all this estimated saving. Scientists are also working on superconductors which save quite a bit of energy, but necessitate very cold temperatures which will become increasingly difficult to maintain.

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    I'm not entirely convinced by your superconductor argument. If the superconductors require cooling to liquid nitrogen or liquid helium boiling temperatures, due to the large temperature difference between these and the ambient temperature, worldwide temperature increase is going to increase nitrogen/helium consumption only very little. I would be more concerned about our helium supplies depleting. – juhist Aug 6 at 8:13
  • no, you are right, I shouldn't have mentioned superconductors. I think the best way to answer the question is to look at where the bulk of the energy using population is distributed around the world. People in cold climates use less heating as the climate warms, in hot climates more air conditioning. So its really a question of weighing energy spent in heating your house against energy spent in cooling it. – animartco Aug 7 at 12:16
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This question seems to have several components.

Firstly, in terms of PV energy production, a rise in temperature would most likely have a slightly negative effect due to decreased efficiency of solar cells at higher temperatures and perhaps an even greater decrease caused by an increase of cloud cover created by oceanic evaporation. On the other hand, an increase in temperature might cause an increase in rainfall, thereby improving the efficiency of hydroelectric power generation.

Secondly, global climate change in general has a wide variety of effects on regional, local, and micro climates, many of which are indirectly influenced by changes in temperature. The various consequences that might be considered "better" are infrequently examined, and I think it is because climate change enthusiasts would be tarred and feathered more adamantly than climate change deniers.

Next, a rise in temperature might be warmly welcomed by those living in colder climates, but there are many other methods to approach our heating/cooling power requirements which are better addressed through other means. For instance, building subterranean or partially underground homes has a huge impact on indoor climate for both Winter and Summer, in both hot and cold climates.

Personally, I've managed comfortably now for a year without any heating or cooling power use at all, but it took ten years to create a comfortable and sustainable micro-climate for myself, my plants, and my livestock. Your question inspires me to explore how I can now use my excess PV power for CCS because it's a shame to see that going to waste.

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