Investigating Past Climates
For centuries, indigenous communities shared oral histories detailing periods of hunger, droughts and great harvest, subconsciously archiving information about climate and environmental change that could help future generations better prepare for periods of droughts, floods or great crop yields. It was a way of building resilience by recording memory archives of past climates. Today, the geoscience branch of paleoclimatology plays this role. Traditional environmental knowledge that is common in indigenous populations is often very regional, specific and tied to known cultural cues. Paleoclimate scientists attempt to capitalise on the efficiency present day technologies and scientific approaches affords them to reconstruct past climates as far back as over 5000 years ago. Their research often focuses on gaining long term perspective on how climate variability affects ecosystems, understanding large scale climate cycles, analyzing regional and global climate sensitivity and discovering climate forcings. If this doesn’t sound clear, it’s because it’s not.
Climate happens over a long period of time. Climate change often manifests itself in the form of extreme weather changes and it is confused for that, but it’s far reaching in terms of geographical impacts as well as time period. Paleoclimate scientists understand that the earth’s climate responds to many atmospheric, land factors and possibly anthropogenic activities very very slowly. From interglacial periods, to El Nino and El Nina periods, the earth’s climate is like a big machine with thousands of tiny cogwheels that are key to the efficient running of the entire system. It is incredibly complex.
Factors affecting climate
Some of the well known factors affecting climate, often at varying intensities include ocean currents- which play a key role in the distribution of heat around the world, changes in volcanic activity- volcanoes often dispel tons of CO2 and SO2 gases into the atmosphere and have been doing that since the earth was only a couple of thousands of years old, the Earth’s orbit and distance from the sun- which affects the degree of solar radiation that enters the planet, earth’s tilt. Regional climate can also be affected by altitude and latitude or distance from the equator and distance from the ocean. All of these are natural causes and lead to regular climate variability that causes the earth to enter periods such as greenhouse and icehouse conditions.
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| Image sourced from http://www.meteorologyclimate.com/climate-variation-factors.htm |
To learn more about the natural factors affecting climate change check out these articles
Separating human influences from natural causes of climate change
Current trends showing the rate at which the planet is warming cannot be solely explained by the natural causes of climate change mentioned above alone. This is because these factors operate on a longer time scale than we are seeing environmental change happen, so scientists like paleoclimate scientist have turned to anthropogenic activities as a possible explanation. Statistics from research and observations back this hypothesis up because over the past 30 years, human factors have contributed significantly to the increase in global temperatures than natural factors. The figure below also supports this assertion. From around 1975 to the 2000s we notice a separation of trends between observed global temperature change and natural factors contributing to increased temperatures. This same conclusion has been reached by many other models that have been computed with different parameters and settings. The only way to explain the rate and magnitude of current global temperature change is by accounting for the impact of greenhouse emissions due to anthropogenic activities.
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Why are we worried about droughts in the Amazon?
In 2005 and 2010 scientists observed declining precipitation rates in some parts of the Amazon rainforests, followed by loss of vegetation and stalled tree growth. The shocking revelation was, parts of the rainforest was going through a drought. Tropical rainforests receive the highest annual rainfall, are home to a significant percentage of the planet’s biodiversity pool and absorb large quantities of atmospheric CO2- acting as carbon sinks. An increase in the frequency of these droughts would likely accelerate global temperatures, even if global stakeholders effectively reduced carbon emissions.
This is why our research is relevant. JHU-L2 and AYC are sediment cores that were acquired from paleolakes in the Amazon. By subsampling them, we are able to compile thousands of years worth of data that can allow us to track environmental change over time in the Amazon. Charcoal is a major paleoclimate proxy that is a great signal for aridity because it is often produced when temperatures are high, vegetation is high and paleowildfires hit. So far we have been able to use CharAnalysis, the peak detection software to identify fire incidents around Lake Ayauchi from as far back as 1000 years ago. Leading us to establish a past record of droughts in the Amazon rainforest and infer that while the 2005 and 2010 droughts are not anomalies, the frequency at which they are happening might be. This calls for more research, many scientists are interested in investigating global and regional climate variability so that they can use their data to design better climate change models that are much more representative of how the climate functions and the complex response mechanisms that are intertwined with climate changes. Others are trying to figure out how resilient tropical rainforest are to climate change and paleodroughts. Environmental changes also often force a change in culture and lifestyle, so Amazonian droughts might affect indigenous communities way of life.
Paleoclimate reconstructions can help us plan and build resilience against environmental change, but importantly they advance our understanding of how the climate works and demand that we make necessary iterations to our current climate models.
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