The overwhelming consensus of the international scientific community is that major climatic changes are now underway across the planet, and that to greater or lesser extents these are being driven by human practices since the late 19th century. Global organisations such as the Intergovernmental Panel on Climate Change (IPCC) and national bodies such as the Meteorological Office National Climate Information Centre have produced recent reports outlining the evidence for climate change and alterations to weather patterns recorded so far (IPCC 2018; Kendon et al. 2018). The Environment Agency and Historic England amongst other organisations have begun to produce guidelines for the likely impact of changes on British landscapes and archaeology (https://historicengland.org.uk/research/current/threats/heritage-climate-change). Climate change is increasingly discussed by many archaeologists, either in terms of new weather patterns and conditions affecting buried and upstanding archaeological remains in Britain and the world (Chapman 2002; Howard et al. 2008), but also how archaeological evidence and palaeo-environmental data might themselves contribute to wider understandings of climate change’s impact on human communities (Sandweiss and Kelley 2012). The West Yorkshire Iron Age and Romano-British Research Agenda (Chadwick 2009: section 11.4) was one of the first such archaeological frameworks to consider the likely impact upon heritage assets at a regional level, but it is now imperative that all such research agendas do so.
In terms of broad climate and weather changes, there will probably be milder but much wetter winters, and longer hotter, drier summers; trends which have already started to become apparent in the past few years (Kendon et al. 2018). Human activities have already caused a mean global temperature rise of c. 1.0°C above pre-industrial levels, with a likely range of 0.8° C to 1.2° C. Global warming is likely to reach 1.5° C between 2030 and 2052 if it continues at the present rate (IPPC 2018: 4), and 2° C by 2100. This might not seem much, but global average temperature rises of 2⁰ C have not occurred on earth for over 100, 000 years and the last such changes led to widespread and highly significant transformations in climate and weather patterns (https://historicengland.org.uk/research/current/threats/heritage-climate-change). July 2019 has been the hottest on record.
Such changes will cause rising sea-levels and greater coastal flooding and erosion. It is also very likely that there will be a greater frequency of extreme weather events. In Britain, upland areas may experience summer droughts, falling water tables and destructive wildfires. At the same time, winters will become milder, but overall there will be an increase in rainfall including more sudden rainstorm events, as warmer air can hold greater moisture (Howard et al. 2008: 407; IPPC 2018: 12). Such events in 2017 have been published by the Met Office (Kendon et al. 2018: 2, 24-7). Total rainfall from extremely wet days has increased by about 17% since the 1960s. Overall seven of the ten wettest years for the UK have occurred since 1998; and current predictions suggest increased storminess in future, with increased likelihood of heavier winds too, though this also occurred during the 1920s. There are significant regional variations to this overall national pattern (Kendon et al. 2018: 12-4). There will likely be more events in northern England such as the destructive floods in York in November 2000 (e.g. Lane 2004: 13-4) and those in Sheffield in June 2007, caused by short periods of extremely intense rainfall leading to dramatic sudden increases in river flows and hence water levels. Low-lying areas alongside the Rivers Don, Rother, Idle and Torne could thus be flooded and damaged, with archaeological deposits or remains either buried by silt and debris or eroded by increased storm surges of current (q.v. Challis, Brown and Kincy 2008; Chapman 2002: 243). This is a very real threat to the possible Roman temple at Bawtry Carr.
In upland areas, streams and runoff could cause great localised erosion, especially where moorlands and hillsides have previously been experiencing prolonged dry spells or have been largely stripped of vegetation by fires. This might affect upland Iron Age and Romano-British fields and enclosures, and those on slopes or with exposed earthworks where erosion has removed grass or other vegetation. This may in turn cause increased flooding within lowland river valleys, and some reclaimed low-lying former alluvial areas may need to be returned to water meadows, osier beds and wetlands (Challis, Brown and Kincy 2008). As Historic England note, both sudden heavy rainfall as well as the cumulative impact from less intense but repeated heavy rainfall events can all be damaging to buried archaeological deposits and remains (https://historicengland.org.uk/research/current/threats/heritage-climate-change). The groundwater chemistry could be altered, and there may be other unpredictable changes to buried waterlogged sites, including Sutton Common. Although the dry summer of 2018 was good for cropmark formation, increasingly saturated soils would make geophysical survey, soil stripping and excavation more problematic at times. Prolonged spells of intense heat and dry conditions would also cause problems for fieldwork.
The many future human responses to climate change in Britain range from increased flood defences and drainage, changes to buildings and in land management and environmental stewardship and changing farming practices (e.g. Howard et al. 2008: 405-6). These might impact directly on archaeological remains. Different crops and/or crop regimes may be required to cope with wider climatic changes, whilst in the future increased quantities of crops could be planted for biofuel production and to be used in biomass generators. These new crops or crop regimes may have unforeseen and highly varied impacts upon buried archaeology than those previously in use. Climate change will also have long-term changes upon energy production and consumption. The need for renewable energy sources may require the construction of wind and solar generation stations. Several wind turbine schemes have already been proposed on hilltop areas in South Yorkshire and have led to archaeological investigations to inform the planning process (e.g. Rose 2010). Careful planning and mitigation will be required to ensure that any negative impacts of future energy production on archaeological assets are minimised.
Following the (probable) withdrawal of the United Kingdom from the European Union in 2019, some small upland livestock farms may go out of business with implications for future land stewardship and management of heritage assets. In the future there may be a perceived need for greater food security and production, and perhaps more intensive arable agriculture. There may be increased political pressure for such intensification. Ploughing is already having a highly deleterious effect upon many South Yorkshire archaeological sites known from cropmarks. Future demand for housing and major infrastructure developments such as the High Speed 2 rail link might also have considerable archaeological implications and impacts upon archaeology in South Yorkshire.
A scoping document could be produced by the South Yorkshire Archaeology Service to establish the possible archaeological implications of climate change, agricultural and developmental impacts within South Yorkshire. The use of GIS as a predictive tool to examine and identify areas likely to be affected by flooding and run-off is also being developed (Cook 2018), which may help with such analyses.