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Even with all humanity’s carbon emissions today. But there is much less carbon dioxide in Earth’s atmosphere than Venus, and the Earth is further away from the Sun. But if carbon emissions continue at current rates, will there be any risk of reaching a tipping point where escaped greenhouse phenomena make the world uninhabitable for all life forms?
When sunlight enters Earth’s atmosphere, some clouds are reflected back into space, some from bright surfaces such as ice and snow, and some are absorbed by the land and ocean surfaces.
To maintain balance, the Earth releases energy back into space in the form of infrared or long wave radiation. Some long-wave radiation is absorbed in the atmosphere by heat-trapping gases such as carbon dioxide.
This is a well known greenhouse effect.
Read more: Climate Explained: What would the Earth be like if we didn’t pump greenhouse gases into the atmosphere?
As a rule of thumb, the increase in carbon dioxide concentrations over the past 250 years has led to an increase in average surface temperatures.
One of the consequences of increasing the concentration of carbon dioxide in the atmosphere is that as the atmosphere warms, more water vapor is generated. Since water vapor is a greenhouse gas, the effect can be expanded.
In general, as the surface temperature increases, the Earth emits more long-wave radiation into space to maintain energy balance, but there is a limit on how much long-wave radiation can be released.
If the atmosphere is completely saturated with water vapor, the Earth’s surface and the lower atmosphere will be warmer. But the emission of long wave radiation cannot be increased any further.
This is called a greenhouse with no escape, and means that the Earth will become fatal and cannot cool itself by releasing heat into space.
In the end, this is the fate of the world. Billions of years from now, the sun will brighten and grow into a red dwarf. As the Sun’s luminosity increase, the Earth warms and the oceans evaporate.
The hot and sweltering atmosphere will ensure that the Earth is not as inhabitable as it is today as it is today Venus.
But can we bring the situation to a shorter time frame through sustained carbon dioxide emissions? The good news is, probably not.
Now we are safe
Previous research has found that due to differences in properties of water vapor and carbon dioxide as a greenhouse gas, increasing atmospheric carbon dioxide is insufficient to produce exhausting greenhouse gases.
At present, atmospheric carbon dioxide is approximately 416 parts per million (ppm) – up from about 280 ppm since the first industrial revolution began about 250 years ago.
In a geologic sense, this is a huge increase that will happen over a short period of time, but human carbon dioxide emissions are considered insufficient to produce exhausting greenhouses due to the existing fossil fuel reserves.
The world should be safe from at least a runaway greenhouse evolving for another 1.5 billion years.
But then …
All of the above caveats are that the models scientists use to study future climates are built on known past conditions. Therefore, it is difficult to predict how certain parts of the climate system might behave under very high greenhouse gas emissions scenarios.
For example, clouds can reflect sunlight back into space, or they can trap the heat emitted by the Earth. In a warming world, scientists are not yet clear what role clouds will play.
Read more: New Zealand normal temperatures are expected to warm up.
While the escaped greenhouse will make the world unable to live fully against life, as we know it, the potential losses from global warming just a few degrees Celsius are serious and must not be mitigated. Price down
The rise in sea level, the increasing frequency and severity of extreme weather events, threats to endangered species and unique ecosystems are just a few of the reasons we need to worry.
The silver lining is that we (probably) don’t need to worry about becoming like our neighbor Venus anytime soon.