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By James Renwick
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 email@example.com
Earth had several periods of high carbon dioxide levels in the atmosphere and high temperatures over the last several million years. Can you explain what caused these periods, given that there was no burning of fossil fuels or other sources of human created carbon dioxide release during those times?
Burning fossil fuels or vegetation is one way to put carbon dioxide into the air – and it is something we have become very good at. Humans are generating nearly 40 billion tons of carbon dioxide every year, mostly by burning fossil fuels.
Natural Changes in Carbon Dioxide<p>Every year, carbon dioxide concentrations rise and fall a little as plants grow in spring and summer and die off in the autumn and winter. The timing of this <a href="https://niwa.co.nz/atmosphere/our-data/trace-gas-plots/carbon-dioxide" target="_blank">seasonal rise and fall</a> is tied to northern hemisphere seasons, as most of the land surface on Earth is there.</p><p>The oceans also play an active role in the carbon cycle, contributing to variations over a few months to slow shifts over centuries. Ocean water takes up carbon dioxide directly in an exchange <a href="https://sos.noaa.gov/datasets/ocean-atmosphere-co2-exchange/" target="_blank">between the air and seawater</a>. Tiny marine plants use carbon dioxide for photosynthesis and many microscopic marine organisms use carbon compounds to make shells. When these marine micro-organisms die and sink to the seafloor, they take the carbon with them.</p><p>Collectively, the biosphere (ecosystems on land and in soils) and the oceans are absorbing about <a href="https://worldoceanreview.com/en/wor-1/ocean-chemistry/co2-reservoir/" target="_blank">half of all human-emitted carbon dioxide</a>, and this slows the rate of climate change. But as the climate continues to change and the oceans warm up further, it is not clear whether the biosphere and oceans will continue absorbing such a large fraction of our emissions. As water warms, it is less able to absorb carbon dioxide, and as the climate changes, many ecosystems become stressed and are less able to photosynthesise carbon dioxide.</p>
Earth’s Deep Climate History<p>On time scales of hundreds of thousands to millions of years, carbon dioxide concentrations in the air have varied hugely, and so has global climate.</p><p>This <a href="https://www.skepticalscience.com/weathering.html" target="_blank">long-term carbon cycle</a> involves the formation and decay of the Earth's surface itself: tectonic plate activity, the build-up and weathering of mountain chains, prolonged volcanic activity, and the emergence of new seafloor at active mid-ocean faults.</p><p>Most of the carbon stored in the Earth's crust is in the form of limestone, created from the carbon-based shells of marine organisms that sank to the ocean floor millions of year ago.</p><p>Carbon dioxide is added to the air when volcanoes erupt, and it is taken out of the air as rocks and mountain ranges weather and wear down. These processes typically take millions of years to add or subtract carbon dioxide from the atmosphere.</p>
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By Malavika Vyawahare
Giant tortoises and flying foxes once roamed La Réunion, a volcanic island off the eastern coast of Africa. Then humans arrived and decided to stay. Within 150 years of their appearance, large fruit-eating animals like the giant tortoises (Cylindraspis indica) and flying foxes (Pteropus niger), a type of bat, were wiped off the face of La Réunion.
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EcoWatch Daily Newsletter
By Jason Bittel
Since Hawaii's Kilauea volcano began erupting in early May, we've been mesmerized, month after month, by videos depicting what can happen when molten rock dances through the air, forms gigantic rivers or crashes into a Ford Mustang.
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On Wednesday the Indonesian government opened an airport on Bali as wind blew away ash spewing out of a volcano, clearing the air for planes and giving residents and tourists a chance to escape.
In the past several days, the volcano has disrupted operations at Bali's airport, the second-busiest in Indonesia, while tens of thousands of residents living within a 10-kilometer radius of Mount Agung have been told to leave. Around 43,000 people had fled, but an estimated 90,000 to 100,000 people were still living in the eruption zone.