In April of this year, the Mauna Loa Observatory in Hawaii recorded an average concentration of atmospheric carbon dioxide above 410 parts per million (ppm). This was the highest monthly average in recorded history, and in fact according to ice core records it is the highest value in at least 800,000 years.
To be clear, I accept the scientific consensus on the impact of a rising atmospheric carbon dioxide concentration. It is a known greenhouse gas, and the mechanism by which greenhouse gases increase the earth's temperature is known. While there are uncertainties in the models -- and these uncertainties are often used to dispute the underlying science -- a constant buildup of greenhouse gases will raise the earth's temperature.
Part of what is unknown about the effect of greenhouse gases on climate is the impact of feedback loops. These can be both positive and negative.
A warming earth can release methane from permafrost. Methane is a powerful greenhouse gas, and that creates a positive feedback loop.
There are also moderating influences like the oceans, which can absorb a certain amount of carbon dioxide. This means that the temperature increase could be less than what might be expected based simply on the amount of carbon dioxide that was released.
The impact of these feedback loops and moderating influences is one reason climate models can be inaccurate.
Even those who don't accept the science behind climate change should be concerned about this rise, because it continues unabated. At what point might it become a concern? 500 ppm? 1,000? If you look at the rate of steady increases, this curve should concern everyone on the planet because the increase is slowly accelerating over time:
The worrisome part is that the trend isn't expected to change anytime soon. Carbon dioxide that is emitted today takes time to accumulate in the atmosphere, and then it remains in the atmosphere for thousands of years.
In any case, there are no signs that what we are emitting is slowing down.
The 2018 BP Statistical Review of World Energy that was released earlier this month showed a new all-time high for global carbon dioxide emissions in 2017, which were 426 million metric tons higher than in 2016. This was 1.6% higher than carbon dioxide emissions in 2016, and was higher than the 10-year average growth rate of 1.3%.
Since the Kyoto Protocol -- the international treaty that commits state parties to reduce greenhouse gas emissions -- went into effect in 2005, global carbon dioxide emissions have increased by 19%.
The countries responsible for the increase in carbon dioxide concentrations have shifted in recent decades. Developed countries are moving away from coal, and toward cleaner natural gas and renewables. Developing countries -- even those that are embracing renewable energy -- emit the most carbon dioxide, and their emissions are growing at the fastest rates in the world.
I will delve deeper into regional and country-level contributions and trends in the next article.